A mountain range or hill range is a series of mountains or hills ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form and alignment that have arisen from the same cause an orogeny. Mountain ranges are formed by a variety of geological processes, but most of the significant ones on Earth are the result of plate tectonics. Mountain ranges are found on many planetary mass objects in the Solar System and are a feature of most terrestrial planets. Mountain ranges are segmented by highlands or mountain passes and valleys. Individual mountains within the same mountain range do not have the same geologic structure or petrology, they may be a mix of different orogenic expressions and terranes, for example thrust sheets, uplifted blocks, fold mountains, volcanic landforms resulting in a variety of rock types. Most geologically young mountain ranges on the Earth's land surface are associated with either the Pacific Ring of Fire or the Alpide Belt.
The Pacific Ring of Fire includes the Andes of South America, extends through the North American Cordillera along the Pacific Coast, the Aleutian Range, on through Kamchatka, Taiwan, the Philippines, Papua New Guinea, to New Zealand. The Andes is 7,000 kilometres long and is considered the world's longest mountain system; the Alpide belt includes Indonesia and Southeast Asia, through the Himalaya, Caucasus Mountains, Balkan Mountains fold mountain range, the Alps, ends in the Spanish mountains and the Atlas Mountains. The belt includes other European and Asian mountain ranges; the Himalayas contain the highest mountains in the world, including Mount Everest, 8,848 metres high and traverses the border between China and Nepal. Mountain ranges outside these two systems include the Arctic Cordillera, the Urals, the Appalachians, the Scandinavian Mountains, the Great Dividing Range, the Altai Mountains and the Hijaz Mountains. If the definition of a mountain range is stretched to include underwater mountains the Ocean Ridges form the longest continuous mountain system on Earth, with a length of 65,000 kilometres.
The mountain systems of the earth are characterized by a tree structure, where mountain ranges can contain sub-ranges. The sub-range relationship is expressed as a parent-child relationship. For example, the White Mountains of New Hampshire and the Blue Ridge Mountains are sub-ranges of the Appalachian Mountains. Equivalently, the Appalachians are the parent of the White Mountains and Blue Ridge Mountains, the White Mountains and the Blue Ridge Mountains are children of the Appalachians; the parent-child expression extends to the sub-ranges themselves: the Sandwich Range and the Presidential Range are children of the White Mountains, while the Presidential Range is parent to the Northern Presidential Range and Southern Presidential Range. The position of mountains influences climate, such as snow; when air masses move up and over mountains, the air cools producing orographic precipitation. As the air descends on the leeward side, it warms again and is drier, having been stripped of much of its moisture.
A rain shadow will affect the leeward side of a range. Mountain ranges are subjected to erosional forces which work to tear them down; the basins adjacent to an eroding mountain range are filled with sediments which are buried and turned into sedimentary rock. Erosion is at work while the mountains are being uplifted until the mountains are reduced to low hills and plains; the early Cenozoic uplift of the Rocky Mountains of Colorado provides an example. As the uplift was occurring some 10,000 feet of Mesozoic sedimentary strata were removed by erosion over the core of the mountain range and spread as sand and clays across the Great Plains to the east; this mass of rock was removed as the range was undergoing uplift. The removal of such a mass from the core of the range most caused further uplift as the region adjusted isostatically in response to the removed weight. Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment.
Computer simulation has shown that as mountain belts change from tectonically active to inactive, the rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides. Mountains on other planets and natural satellites of the Solar System are isolated and formed by processes such as impacts, though there are examples of mountain ranges somewhat similar to those on Earth. Saturn's moon Titan and Pluto, in particular exhibit large mountain ranges in chains composed of ices rather than rock. Examples include the Mithrim Montes and Doom Mons on Titan, Tenzing Montes and Hillary Montes on Pluto; some terrestrial planets other than Earth exhibit rocky mountain ranges, such as Maxwell Montes on Venus taller than any on Earth and Tartarus Montes on Mars, Jupiter's moon Io has mountain ranges formed from tectonic processes including Boösaule Montes, Dorian Montes, Hi'iaka Montes and Euboea Montes. Peakbagger Ranges Home Page Bivouac.com
The Viceroyalty of New Spain was an integral territorial entity of the Spanish Empire, established by Habsburg Spain during the Spanish colonization of the Americas. It covered a huge area that included territories in North America, South America and Oceania, it originated in 1521 after the fall of Mexico-Tenochtitlan, the main event of the Spanish conquest, which did not properly end until much as its territory continued to grow to the north. It was created on 8 March 1535 as a viceroyalty, the first of four viceroyalties Spain created in the Americas, its first viceroy was Antonio de Mendoza y Pacheco, the capital of the viceroyalty was Mexico City, established on the ancient Mexico-Tenochtitlan. It included what is now Mexico plus the current U. S. states of California, Colorado, New Mexico, Texas, Washington and parts of Idaho, Wyoming, Kansas and Louisiana. The political organization divided the viceroyalty into captaincies general; the kingdoms were those of New Spain. There were four captaincies: Captaincy General of the Philippines, Captaincy General of Cuba, Captaincy General of Puerto Rico and Captaincy General of Santo Domingo.
These territorial subdivisions had a captain general. In Guatemala, Santo Domingo and Nueva Galicia, these officials were called presiding governors, since they were leading royal audiences. For this reason, these hearings were considered "praetorial." There were two great estates. The most important was the Marquisate of the Valley of Oaxaca, property of Hernán Cortés and his descendants that included a set of vast territories where marquises had civil and criminal jurisdiction, the right to grant land and forests and within which were their main possessions; the other estate was the Duchy of Atlixco, granted in 1708, by King Philip V to José Sarmiento de Valladares, former viceroy of New Spain and married to the Countess of Moctezuma, with civil and criminal jurisdiction over Atlixco, Guachinango and Tula de Allende. King Charles III introduced reforms in the organization of the viceroyalty in 1786, known as Bourbon reforms, which created the intendencias, which allowed to limit, in some way, the viceroy's attributions.
New Spain developed regional divisions, reflecting the impact of climate, indigenous populations, mineral resources. The areas of central and southern Mexico had dense indigenous populations with complex social and economic organization; the northern area of Mexico, a region of nomadic and semi-nomadic indigenous populations, was not conducive to dense settlements, but the discovery of silver in Zacatecas in the 1540s drew settlement there to exploit the mines. Silver mining not only became the engine of the economy of New Spain, but vastly enriched Spain and transformed the global economy. New Spain was the New World terminus of the Philippine trade, making the viceroyalty a vital link between Spain's New World empire and its Asian empire. From the beginning of the 19th century, the viceroyalty fell into crisis, aggravated by the Peninsular War, its direct consequence in the viceroyalty, the political crisis in Mexico in 1808, which ended with the government of viceroy José de Iturrigaray and gave rise to the Conspiracy of Valladolid and the Conspiracy of Querétaro.
This last one was the direct antecedent of the Mexican War of Independence, when concluding in 1821, disintegrated the viceroyalty and gave way to the Mexican Empire, in which Agustín de Iturbide would be crowned. The Kingdom of New Spain was established following the Spanish conquest of the Aztec Empire in 1521 as a New World kingdom dependent on the Crown of Castile, since the initial funds for exploration came from Queen Isabella. Although New Spain was a dependency of Spain, it was a kingdom not a colony, subject to the presiding monarch on the Iberian Peninsula; the monarch had sweeping power in the overseas territories,The king possessed not only the sovereign right but the property rights. Every privilege and position, economic political, or religious came from him, it was on this basis that the conquest and government of the New World was achieved. The Viceroyalty of New Spain was established in 1535 in the Kingdom of New Spain, it was the first New World viceroyalty and one of only two in the Spanish empire until the 18th century Bourbon Reforms.
The Spanish Empire comprised the territories in the north overseas'Septentrion', from North America and the Caribbean, to the Philippine and Caroline Islands. At its greatest extent, the Spanish crown claimed on the mainland of
Endemism is the ecological state of a species being unique to a defined geographic location, such as an island, country or other defined zone, or habitat type. The extreme opposite of endemism is cosmopolitan distribution. An alternative term for a species, endemic is precinctive, which applies to species that are restricted to a defined geographical area; the word endemic is from New Latin endēmicus, from Greek ενδήμος, endēmos, "native". Endēmos is formed of en meaning "in", dēmos meaning "the people"; the term "precinctive" has been suggested by some scientists, was first used in botany by MacCaughey in 1917. It is the equivalent of "endemism". Precinction was first used by Frank and McCoy. Precinctive seems to have been coined by David Sharp when describing the Hawaiian fauna in 1900: "I use the word precinctive in the sense of'confined to the area under discussion'...'precinctive forms' means those forms that are confined to the area specified." That definition excludes artificial confinement of examples by humans in far-off botanical gardens or zoological parks.
Physical and biological factors can contribute to endemism. The orange-breasted sunbird is found in the fynbos vegetation zone of southwestern South Africa; the glacier bear is found only in limited places in Southeast Alaska. Political factors can play a part if a species is protected, or hunted, in one jurisdiction but not another. There are two subcategories of endemism: neoendemism. Paleoendemism refers to species that were widespread but are now restricted to a smaller area. Neoendemism refers to species that have arisen, such as through divergence and reproductive isolation or through hybridization and polyploidy in plants. Endemic types or species are likely to develop on geographically and biologically isolated areas such as islands and remote island groups, such as Hawaii, the Galápagos Islands, Socotra. Hydrangea hirta is an example of an endemic species found in Japan. Endemics can become endangered or extinct if their restricted habitat changes, particularly—but not only—due to human actions, including the introduction of new organisms.
There were millions of both Bermuda petrels and "Bermuda cedars" in Bermuda when it was settled at the start of the seventeenth century. By the end of the century, the petrels were thought extinct. Cedars ravaged by centuries of shipbuilding, were driven nearly to extinction in the twentieth century by the introduction of a parasite. Bermuda petrels and cedars are now rare. Principal causes of habitat degradation and loss in endemistic ecosystems include agriculture, urban growth, surface mining, mineral extraction, logging operations and slash-and-burn agriculture
San Bernardino National Forest
The San Bernardino National Forest is a United States National Forest in Southern California encompassing 823,816 acres of which 677,982 acres are federal. The forest is made up of two main divisions, the eastern portion of the San Gabriel Mountains and the San Bernardino Mountains on the easternmost of the Transverse Ranges, the San Jacinto and Santa Rosa Mountains on the northernmost of the Peninsular Ranges. Elevations range from 2,000 to 11,499 feet; the forest includes seven wilderness areas: San Gorgonio, San Jacinto, South Fork San Jacinto, Santa Rosa, Cahuilla Mountain and Bighorn Mountain. Forest headquarters are located in the city of San Bernardino. There are district offices in Lytle Creek and Fawnskin; this site was the filming location for Daniel Boone in 1936. Free camping is available at 47 different'Yellow Post' campsites located throughout the forest. According to United States Geological Survey maps of the forest, it consists of two large areas or tracts: a northern and southern portion.
The west border of the forest adjoins Angeles National Forest and runs north-south about ten miles west of Interstate 15. At its widest parts, the northern portion of the forest runs about 57 miles on an east–west dimension, it runs about 24 miles on a north–south dimension. This portion of the forest encompasses the San Bernardino Mountains; the area extends west of Mount San Wrightwood in San Bernardino County. The eastern portion of the forest extends about ten miles east of Big Bear City and includes the San Gorgonio Wilderness; the southernmost portion is bisected by the Riverside County line and borders the Morongo Indian Reservation north of Cabazon. At its widest point, the southern portion is about 27 miles on a north-south dimension and about 30 miles on an east-west dimension. Toro Peak and the Santa Rosa Indian Reservation are near the south extent. At the north is the Morongo Indian Reservation. Mount San Jacinto State Wilderness is carved out of the southern portion; the community of Idyllwild is surrounded by national forest lands.
While most National Forests include lumber resources, these two areas include: Residential communities and resorts Indian resources such as important caves and pictographs The University of California-owned James Reserve research stationThe two tallest waterfalls in Southern California, Big Falls and Bonita Falls, are located in the San Bernardino National Forest. There are seven official wilderness areas lying within San Bernardino National Forest that are part of the National Wilderness Preservation System. One extends into neighboring Angeles National Forest and three into land, managed by the Bureau of Land Management. Bighorn Mountain Wilderness Cahuilla Mountain Wilderness Cucamonga Wilderness San Gorgonio Wilderness San Jacinto Wilderness Santa Rosa Wilderness South Fork San Jacinto Wilderness The five-member crew of the San Bernardino National Forest Alandale Fire Station's Engine 57 was fatally burned by a sudden, intense fire run up a steep drainage below their location during the Esperanza Fire at 7:15 a.m. on October 26, 2006.
All five firefighters were overrun by the fire at Twin Pines, located in the San Jacinto Mountains four miles southwest of the City of Cabazon, California. The fire was located near California in Riverside County. Alandale station is located near the community of Idyllwild; as of 2001, eight Air Tactical Group Supervisors work out of the Forest Supervisor's Office in San Bernardino. This position requires completion of an 80-hour CDF/Forest Service attack management course. A Helicopter Coordinator course is recommended. There are many different species of many coniferous, that grow in the mountains. Pines, such as ponderosa pine, Jeffrey pine, sugar pine, Coulter pine, lodgepole pine, single-leaf pinyon, knobcone pine all thrive here. Other coniferous trees, such as white fir, bigcone Douglas-fir, incense cedar, western juniper thrive here. Canyon live oak, California black oak, Pacific dogwood are other trees that grow here; the forest contains an estimated 87,400 acres of old growth. The most common old-growth forest types are Sierra Nevada mixed conifer forests, white fir forests, Jeffrey pine forests, lodgepole pine forests.
Big Bear Lake Deep Creek Hot Springs Big Bear Discovery Center Fires in San Bernardino National Forest Valley Fire Cranston Fire Yellow Post Camp Site Info Dated Feb 2014 https://commons.wikimedia.org/wiki/File:Yellow_camp_site_info_big_bear.pdf Official San Bernardino National Forest website Local Hikes.com: Southern California Trails in the San Bernardino National Forest Off-Road Trails in the San Bernardino National Forest SBNF Supervisor's webpage
Desert bighorn sheep
Desert bighorn sheep is a subspecies of bighorn sheep, native to the deserts of the USA's intermountain west and southwestern regions, as well as northwestern Mexico. The trinomial of this species commemorates the American naturalist Edward William Nelson; the characteristics and behavior of desert bighorn sheep follow those of other bighorn sheep, except for adaptation to the lack of water in the desert. They can go for extended periods of time without drinking water; the desert bighorn sheep is the mascot of the Universidad Autónoma de Baja California. The range of Desert bighorn sheep includes habitats in the Mojave Desert, Colorado Desert, Sonoran Desert. Anza-Borrego Desert State Park, Joshua Tree National Park, Death Valley National Park, Kofa National Wildlife Refuge, Cabeza Prieta National Wildlife Refuge, Mojave National Preserve all offer protected habitat for this animal. Populations of the desert bighorn sheep declined drastically with European colonization of the American Southwest beginning in the 16th century.
These declines were followed by a period of population stabilization ascribed to conservation measures. As of 2004, desert bighorn sheep numbers remained low, although the overall population trend had increased since 1960. Desert bighorn sheep are heavy-bodied sheep, similar in size to mule deer. Weights of mature rams range from 115 to 280 pounds. Due to their unique concave elastic hooves, bighorn are able to climb the steep, rocky terrain of the desert mountains with speed and agility, they rely on their keen eyesight to detect potential predators, such as mountain lions and bobcats, they use their climbing ability to escape. Both genders develop horns soon after birth, with horn growth continuing more or less throughout life. Older rams have curling horns measuring over three feet long with more than one foot of circumference at the base; the ewes' horns do not tend to curl. After eight years of growth, the horns of an adult ram may weigh more than 30 pounds. Annual growth rings indicate the animal's age.
The rams may rub their own horns to improve their field of view. Both rams and ewes use their horns as tools to break open cactus, which they consume, for fighting. Desert bighorn sheep live for 10–20 years; the typical diet of a desert bighorn sheep is grasses. When grasses are unavailable, they turn to other food sources, such as forbs, or cacti; the desert bighorn has become well adapted to living in the desert heat and cold and, unlike most mammals, their body temperature can safely fluctuate several degrees. During the heat of the day, they rest in the shade of trees and caves. Southern desert bighorn sheep are adapted to a desert mountain environment with little or no permanent water; some may go without visiting water for weeks or months, sustaining their body moisture from food and from rainwater collected in temporary rock pools. They may have the ability to lose up to 30% of their body weight and still survive. After drinking water, they recover from their dehydrated condition. Wildlife ecologists are just beginning to study the importance of this adaptive strategy, which has allowed small bands of desert bighorns to survive in areas too dry for many of their predators.
Desert bighorn sheep are social. Rams battle to determine the dominant animal, which gains possession of the ewes. Facing each other, rams charge head-on from distances of 20 ft or more, crashing their massive horns together with tremendous impact, until one or the other ceases. Bighorn sheep live in separate ewe bands most of the year, they gather during the breeding season, but breeding may occur anytime in the desert due to suitable climatic conditions. Gestation lasts 150–180 days, the lambs are born in late winter; the number of desert bighorn sheep in North America in pristine times is unknown, but most was in the tens of thousands. In 1929, E. T. Seton estimated the pre-Columbian numbers of all subspecies of bighorn sheep in North America at 1.5-2.0 million. By 1960, the overall bighorn population in the United States, including desert bighorns, had dwindled to 15,000-18,200. Buechner documented major declines from the 1850s to the early 20th century; these declines were attributed to excessive hunting.
In 1939, after intense lobbying by Frederick Russell Burnham and the Arizona Boy Scouts, President Franklin D. Roosevelt signed a proclamation to establish two desert areas in southwestern Arizona to help preserve the desert bighorn sheep: Cabeza Prieta National Wildlife Refuge and the Kofa National Wildlife Refuge. In 1941, the San Andres National Wildlife Refuge in New Mexico was added. Desert bighorn sheep populations have trended upward since the 1960s when their population was estimated at 6,700-8,100; the upward trend was caused including habitat preservation. In 1980, desert bighorn sheep populations were estimated at 8,415-9,040. A state-by-state survey was conducted a few years and estimated the overall US desert bighorn sheep population at 15,980; the 1993 estimate of the population is 18,965-19,040. The results of the state-by-state survey are shown to the right. In southern California, by 1998, only 280 individuals of the peninsular bighorn sheep population remained, that population was added to the list of the United States' most imperiled species.
Populations in three so
Washingtonia filifera known as desert fan palm, California fan palm or California palm, is a flowering plant in the palm family native to the far southwestern United States and Baja California. Growing to 15–20 m tall by 3–6 m broad, it is an evergreen monocot with a tree-like growth habit, it has waxy, fan-shaped leaves. Other common names include California fan petticoat palm; the specific epithet filifera means "thread-bearing". W. filifera is the only palm native to the Western United States and the country's largest native palm. Primary populations are found in desert riparian habitats at spring-fed and stream-fed oases in the Colorado Desert and at a few scattered locations in the Mojave Desert, it is found near watercourses in the Sonoran Desert along the Gila River in Yuma, along the Hassayampa River and near New River in Maricopa County, in portions of Pima County, Pinal County, Mohave County, several other isolated locations in Clark County, Nevada. It is a naturalized species in the warm springs near Death Valley and in the extreme northwest of Sonora.
It is reportedly naturalized in the Southeast, Hawaii, the U. S. Virgin Islands, Australia. W. filifera grows to 18 m in height in ideal conditions. The California fan palm is known as the desert fan palm, American cotton palm, Arizona fan palm; the fronds are up to 4 m long, made up of a petiole up to 2 m long, bearing a fan of leaflets 1.5–2.0 m long. They have long, thread-like, white fibers, the petioles are pure green with yellow edges and filifera-filaments, between the segments; the trunk is gray and tan, the leaves are gray green. When the fronds die, they remain drop down to cloak the trunk in a wide skirt; the shelter that the skirt creates provides a microhabitat for invertebrates. If any red color is present on petioles or trunk, it is not a pure W. filifera, but a W. fila-busta hybrid. W. filifera lives from 80 to 250 years or more. Desert fan palms provide habitat for the giant palm-boring beetle, western yellow bat, hooded oriole, many other bird species. Hooded orioles places to build nests.
Numerous insect species visit the hanging inflorescences. The palm boring beetle Dinapate wrightii can chew through the trunks of other palms. A continued infestation of beetles can kill various genera and species of palms. W. filifera appears to be resistant to the red palm weevil via a mechanism of antibiosis — production of compounds lethal to the larvae. The desert fan palm is experiencing a population and range expansion due to global warming or removing excess mustangs. Natural oases are restricted to areas downstream from the source of hot springs, though water is not always visible at the surface. Grazing animals can kill young plants through trampling, or by eating the terminus at the apical meristem, the growing portion of the plant; this may have kept palms restricted to a lesser range than indicated by the availability of water. Today's oasis environment may have been protected from colder climatic changes over the course of its evolution. Thus, this palm is restricted by both water and climate to separated relict groves.
The trees in these groves show little if any genetic differentiation, suggesting that the genus is genetically stable. Joshua Tree National Park in the Mojave Desert preserves and protects healthy riparian palm habitat examples in the Little San Bernardino Mountains, westward where water rises through the San Andreas Fault on the east valley side. In the central Coachella Valley, the Indio Hills Palms State Reserve and nearby Coachella Valley Preserve, other large oases are protected and accessible; the Santa Rosa and San Jacinto Mountains National Monument, Anza-Borrego Desert State Park both have large and diverse W. filifera canyon oasis habitats. The fruit of the fan palm was eaten raw, cooked, or ground into flour for cakes; the Cahuilla and related tribes used the leaves to make sandals, thatch roofs, baskets. The stems were used to make cooking utensils; the Moapa band of Paiutes and other Southern Paiutes have written memories of using this palm's seed, fruit, or leaves for various purposes including starvation food.
W. filifera is cultivated as an ornamental tree. It is one of the hardiest Coryphoidiae palms, rated as hardy to USDA hardiness zone 8, it can survive brief temperatures of −10 °C with minor damage, established plants have survived, with severe leaf damage, brief periods as low as −12 °C. The plants grow best in Mediterranean climates, but can be found in humid subtropical climates such as eastern Australia and the southeastern USA, it has gained the Royal Horticultural Society's Award of Garden Merit. Johnson. "Washingtonia filifera". IUCN Red List of Threatened Species. Version 2006. International Union for Conservation of Nature. Retrieved 11 May 2006. Floridata.com: Washingtonia filifera Cornett, J. W. 2010. Desert Palm Oasis. Nature Trails Press, Palm Springs, California. Interactive Distribution Map for Washingtonia filifera USDA Plants Profile: Washingtonia filifera UC Jepson Manual treatment — Washingtonia filifera Calflora Database: Washingtonia filifera Washingtonia filifera in Flora of North America Washingtonia filifera — U.
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Imperial County, California
Imperial County is a county in the U. S. state of California. As of the 2010 census, the population was 174,528; the county seat is El Centro. Established in 1907 from a division of San Diego County, it was last county to be formed in California. Imperial County includes California Metropolitan Statistical Area, it is part of the Southern California border region, the smallest but most economically diverse region in the state. It is located in the Imperial Valley, in the far southeast of California, bordering both Arizona and the Mexican state of Baja California. Although this region is a desert, with high temperatures and low average rainfall of three inches per year, the economy is based on agriculture due to irrigation, supplied wholly from the Colorado River via the All-American Canal; the Imperial Valley is divided between the United States and Mexico, Imperial County is influenced by Mexican culture. 80% of the county's population is Hispanic, with the vast majority being of Mexican origin.
The remainder of the population is predominantly non-Hispanic white as well as smaller African American, Native American and Asian minorities. In 2016, Imperial County had the highest percentage of unemployed people of any county in the United States, at 23.5%. Spanish explorer Melchor Díaz was one of the first Europeans to visit the area around Imperial Valley in 1540; the explorer Juan Bautista de Anza explored the area in 1776. Years after the Mexican–American War, the northern half of the valley was annexed by the U. S. while the southern half remained under Mexican rule. Small scale settlement in natural aquifer areas occurred in the early 19th century, but most permanent settlement was after 1900. In 1905, torrential rainfall in the American Southwest caused the Colorado River to flood, including canals, built to irrigate the Imperial Valley. Since the valley is below sea level, the waters never receded, but collected in the Salton Sink in what is now called the Salton Sea. Imperial County was formed in 1907 from the eastern portion of San Diego County.
The county took its name from Imperial Valley, itself named for the Imperial Land Company, a subsidiary of the California Development Company, which at the turn of the 20th century had claimed the southern portion of the Colorado Desert for agriculture. Much of the Imperial Land Company's land existed in Mexico; the objective of the company was commercial crop farming development. By 1910, the land company had managed to settle and develop thousands of farms on both sides of the border; the Mexican Revolution soon after disrupted the company's plans. Nearly 10,000 farmers and their families in Mexico were ethnically cleansed by the rival Mexican armies. Not until the 1920s was the other side of California in America sufficiently peaceful and prosperous for the company to earn a return for a large percentage of Mexicans, but some chose to stay and lay down roots in newly sprouted communities in the valley; the county experienced a period of migration of "Okies" from drought-trodden dust bowl farms by the need of migrant labor, prosperous job-seekers alike from across the U.
S. arrived in the 1930s and 1940s in World War II and after the completion of the All American Canal from its source, the Colorado River, from 1948 to 1951. By the 1950 census, over 50,000 residents lived in Imperial County alone, about 40 times that of 1910. Most of the population was year-round but would increase every winter by migrant laborers from Mexico; until the 1960s, the farms in Imperial County provided substantial economic returns to the company and the valley. El Centro has one of the highest unemployment rates in the U. S. and ranks one of California's poorest counties or have a lower than state and national average annual household income. Fort Yuma is located on the banks of the Colorado River in California. First established after the end of the Mexican–American War in 1848, it was located in the bottoms near the Colorado River, less than 1 mile below the mouth of the Gila River, it was to defend the newly settled community of Yuma, Arizona on the other side of the Colorado River and the nearby Mexican border.
In March 1851 the post was moved to a small elevation on the Colorado's west bank, opposite the present city of Yuma, Arizona, on the site of the former Mission Puerto de Purísima Concepción. This site had been occupied by Camp Calhoun, named for John C. Calhoun, established in 1849. Fort Yuma was established to protect the southern emigrant travel route to California and to attempt control of the Yuma Indians in the surrounding 100-mile area. NAF El Centro is the winter home of the U. S. Navy Flight Demonstration Squadron, The Blue Angels. NAF El Centro kicks off the Blue Angels' season with their first air show, traditionally held in March. Imperial, CA is home to the California Mid-Winter Fair and Fiesta, the local county fair, held in late February to early March, it is home to the Imperial Valley Speedway, a race track of 3⁄8 mile. The name Algodones Dunes refers to the entire geographic feature, while the administrative designation for that portion managed by the Bureau of Land Management is the "Imperial Sand Dunes Recreation Area".
The Algodones Sand Dunes are the largest mass of sand dunes in California. This dune system extends for more than 40 miles along the eastern edge of the Imperial Valley agricultural region in a band averaging 5 miles in width. A major east-west route of the Union Pacific railroad skirts the e