Yuma is a city in and the county seat of Yuma County, United States. The city's population was 93,064 at the 2010 census, up from the 2000 census population of 77,515. Yuma is the principal city of the Yuma, Metropolitan Statistical Area, which consists of Yuma County. According to the United States Census Bureau, the 2014 estimated population of the Yuma MSA is 203,247. More than 85,000 retirees make Yuma their winter residence. Yuma is in the Sonoran Desert, Yuma Desert sub-region; the area's first settlers for thousands of years were historic tribes. Their descendants now occupy the Quechan reservations. In 1540, Spanish colonial expeditions under Hernando de Alarcon and Melchior Diaz visited the area and recognized the natural crossing of the Colorado River as an ideal spot for a city; the Colorado River narrows to under 1,000 feet wide in one area. Military expeditions that crossed the Colorado River at the Yuma Crossing include Juan Bautista de Anza, the Mormon Battalion and the California Column.
During and after the California Gold Rush to the late 1870s, the Yuma Crossing was known for its ferry crossings for the Southern Emigrant Trail. This was considered the gateway to California, as it was one of the few natural spots where travelers could cross the otherwise wide Colorado River. Following the United States establishing Fort Yuma, two towns developed one mile downriver; the one on the California side was called Jaeger City, named after the owner of Jaeger's Ferry, which crossed the river there. It was for a time the larger of the two, with the Butterfield Overland Mail office and station, two blacksmiths, a hotel, two stores, other dwellings; the other was called Colorado City. Developed on the south side of the river in what is now Arizona by speculator Charles Poston, it was the site of the custom house; when started, it was just north of the border between Mexican-ruled Sonora and California. After the Gadsden Purchase by the United States, the town bordered on the Territory of New Mexico.
This area was designated as the Territory of Arizona in 1863. The Colorado City site at the time was duly registered in San Diego; the county of San Diego collected taxes from there for many years. From 1853 a smaller settlement, Arizona City, grew up on the high ground across from the fort and was organized under the name of its post office in 1858, it had two stores and two saloons. Colorado City and Jaeger City were completely destroyed by the Great Flood of 1862 and had to be rebuilt on higher ground. At that time Colorado City became part of Arizona City, it took the name Yuma in 1873. From 1854, Colorado City was the major steamboat stop for traffic down the Colorado River. After the 1862 flood, it became part of Arizona City; the steamboats transported passengers and equipment for the various mines and military outposts along the Colorado. They offloaded the cargo from ships at the mouth of the Colorado River at Robinson's Landing and from 1864 at Port Isabel. From 1864, the Yuma Quartermaster Depot, today a state historic park, supplied all forts in present-day Arizona, as well as large parts of Colorado and New Mexico.
After Arizona became a separate territory, Yuma became the county seat for Yuma County in 1871, replacing La Paz, the first seat. The Southern Pacific Railroad bridged the river in 1877, acquired George Alonzo Johnson's Colorado Steam Navigation Company, the only steamboat company on the river. Yuma became the new base of navigation on the river, ending the need for Port Isabel, abandoned in 1879; the warehouses and shipyard there were moved to Yuma. The city of Yuma operates as a charter city under the Charter of the City of Yuma; the elected government of the city is the City Council which follows the mayor–council government system and whose members include: The Mayor of the City of Yuma acts as the chief executive officer of the city, is elected for a period of four years. The mayor is elected from the city at large; the mayor has the following powers and responsibilities: act as an ex officio chairman of the city council and preside over meetings, administer oaths and issue proclamations.
The mayor is recognized as the official head of the city by the courts and has the power to take command of the police and govern the city by proclamation during times of great danger. The City of Yuma City Council is the governing body of the City of Yuma and is vested with all powers of legislation in municipal affairs; the council is composed of six council members elected from the city at large for four-year terms, as well as the Mayor of Yuma. A deputy mayor is elected by the Council who shall act as Mayor during the temporary absence of the mayor; the current council members are Gary Knight, Leslie McClendon, Jacob Miller, Edward Thomas, Mike Shelton, Karen Watts. The next election is the August 2019 Primary for the three city council seats that are held by Miller and Shelton; the City Council appoints a city administrator who acts as the chief administrative officer of the city. The city administrator is directly responsible to the City Council for the administration of all city affairs placed in his charge by the City Charter, or by ordinances passed by the Council.
Some of the administrator's duties include: see that all laws and provisions of the City Charter are faithfully executed and submit the annual budget and capital
Course of the Colorado River
The Colorado River is a major river of the western United States and northwest Mexico in North America. Its headwaters are in the Rocky Mountains. Located in north central Colorado it flows southwest through the Colorado Plateau country of western Colorado, southeastern Utah and northwestern Arizona where it flows through the Grand Canyon, it turns south near Las Vegas, forming the Arizona–Nevada border in Lake Mead and the Arizona–California border a few miles below Davis Dam between Laughlin and Needles, California California before entering Mexico in the Colorado Desert. Most of its waters are diverted into the Imperial Valley of Southern California. In Mexico its course forms the boundary between Sonora and Baja California before entering the Gulf of California; this article describes most of the major features along the river. The Colorado River rises on the Continental Divide at La Poudre Pass, in Rocky Mountain National Park, about 40 km north of Lake Granby, as a tiny stream draining a wet meadow.
At the river's headwater, the Continental Divide forms the boundary between the Gulf of Mexico and Pacific Ocean watersheds of North America, between Colorado's Grand and Larimer counties, the northern boundary of Rocky Mountain National Park. The river's first diversion is here at its headwater; the Grand Ditch redirects water from the Never Summer Mountains, which would have flowed into the Colorado River, to instead flow across the divide through La Poudre Pass to irrigate farmland to the east. About a mile downstream from its source, the Colorado River has carved its first canyon, the narrow, deep Little Yellowstone Canyon, it flows through the broad Kawuneeche Valley, where it is joined by U. S. Highway 34, which will parallel it to the town of Granby, it exits Rocky Mountain National Park, flowing into Shadow Mountain Lake and into Lake Granby, which are portions of the Colorado-Big Thompson Project, a large trans-basin water storage and delivery project that diverts water from the Colorado River under the Front Range mountains to provide an agricultural and municipal water supply for the northern Front Range and plains of Colorado.
Starting in Granby, the river is paralleled by U. S. Highway 40 to the town of Kremmling, by the tracks of the Union Pacific Railroad until about the Utah border, carrying the Amtrak California Zephyr passenger train; the canyons and valleys of the Upper Colorado River are among the scenic attractions for passengers on this rail route. Just downstream from Granby, the Colorado is joined by the Fraser River and flows through Windy Gap Reservoir, where more water is diverted to the Front Range via the Windy Gap Project. At Hot Sulphur Springs the river flows through Byers Canyon and is joined by the Williams Fork from the left and Muddy Creek from the right shortly thereafter. Just below Kremmling it is joined by the Blue River from the left before flowing through Gore Canyon, famous for its challenging rapids for the sport of whitewater rafting, where it drops until State Highway 131 crosses at the village of State Bridge, where the Piney River joins from the left; the Eagle River joins from the left in the town of Dotsero, from where Interstate 70 will parallel the Colorado until it enters Utah.
Below Dotsero the Colorado flows through Glenwood Canyon, emerging at the city of Glenwood Springs where the swift flowing Roaring Fork River, its second largest tributary in Colorado joins from the left. West of Glenwood Springs, the Colorado runs through a wider valley along the northern foothills of the Grand Mesa, passing the towns of New Castle, Rifle and De Beque, it flows through De Beque Canyon, where it is joined by Plateau Creek. The Colorado enters the Grand Valley, where its waters are used to irrigate over 40,000 acres of agricultural land. Here it passes Grand Junction, the largest town on the upper Colorado, where it is joined by the Gunnison River, its largest tributary within Colorado and second largest overall; the Gunnison drains from the northern San Juan Mountains, Elk Mountains and Sawatch Range – which includes Colorado's highest peak, 14,440-foot Mount Elbert – and carves the Black Canyon of the Gunnison before joining the Colorado. In the Grand Valley the Colorado becomes a meandering river in contrast to the steep mountain canyons above Grand Junction.
It ranges from 6 to 30 ft in depth with occasional deeper areas. From there the Colorado turns northwest, past Fruita and entering Ruby Canyon as it approaches the Colorado Plateau, it turns southwest once again just before entering Utah. In Utah the Colorado enters the high desert canyon country of the Colorado Plateau, flowing swiftly southwest through Westwater Canyon. Near Dewey it picks up the Dolores River, which together with its tributary the San Miguel drains the western slope of the San Juan Mountains, it passes the Fisher Towers and forms part of the southern border of Arches National Park before entering the Moab Valley at Moab. Just below Moab it carves through a 1,000-foot deep mountain pass known as "The Portal"; the Colorado passes by Dead Horse Point State Park before entering the backcountry of Canyonlands National Park where it is joined from the north by the Green River, its biggest tributary. The Green, flowing from the Wind River Range of western Wyoming, drains 48,000 square miles in southwest Wyoming, northeast Utah and northwest Colorado.
It is much longer than the Colorado above their confluence and carries a larger load of silt, though the Colorado has a greater flow. Before an act of Congress changed the name in 1921 this confluence marked the official beginning of the Colorado River prop
The All-American Canal is an 80-mile long aqueduct, located in southeastern California. It conveys water from the Colorado River to nine cities, it is the Imperial Valley's only water source, replaced the Alamo Canal, located in Mexico. The Imperial Dam, about 30 miles northeast of Yuma, Arizona on the Colorado River, diverts water into the All-American Canal, which runs to just west of Calexico, California before its last branch heads north into the Imperial Valley. Five smaller canals branching off the All American Canal move water into the Imperial Valley; these canal systems irrigate up to 630,000 acres of crop land and have made possible a increased crop yield in this area one of the driest on earth. It is the largest irrigation canal in the world, carrying a maximum of 26,155 cubic feet per second. Agricultural runoff from the All American Canal drains into the Salton Sea; the All American Canal runs parallel to the Mexico California border for several miles. With over 500 people having drowned in the canal since its completion, it has been called "the Most Dangerous Body of Water in the U.
S."The California Office of Environmental Health Hazard Assessment has issued an advisory for any fish caught in the All-American Canal due to elevated levels of mercury, PCBs, selenium. The All-American Canal was authorized along with the Hoover Dam by the 1928 Boulder Canyon Project Act and built in the 1930s by the United States Bureau of Reclamation and Six Companies, Inc.. Its design and construction was supervised by the Bureau's chief designing engineer, John L. Savage and was completed in 1942; the Bureau of Reclamation owns the canal. Water for the canal is diverted at the Imperial Diversion Dam; the All-American Canal feeds, from east to west, the Coachella Canal, East Highline Canal, Central Main Canal, the Westside Main Canal. These five main branches of the canal and a network of smaller canals reduce the flow of the All-American Canal until it ends at a small drop in the western Imperial Valley where it drains into the Westside Main Canal; the main canal is 82 miles, with a total drop of 175 feet, a width of 150 feet to 700 feet and a depth of 7 feet to 50 feet The canals get smaller as they run west because they carry less water.
Eight hydroelectric power plants have been constructed along drops in the All-American Canal system. Drops 1 through 5, Pilot Knob, East Highline and Double Weir are located on the All-American Canal. Another power plant, Turnip, is located on the Central Main Canal branch; the power plants are all small and have a combined capacity of 58 MW. Electricity generation is dictated by water delivery needs. There is a 7.2 MW pumped storage plant at Senator Wash Dam. Water from the Senator Wash Reservoir is released. Runoff from the farmland irrigated by the All-American Canal make up most of the flows in the Alamo River and New River, both of which drain into the Salton Sea, now providing most of its water; the rest is from drainage systems. The Salton Sea had been periodically flooded by extreme Colorado River floods and dried up before being reflooded. If not for the All-American Canal, the Salton Sea would have dried up long ago; the system transports silt and salts from the Colorado River into the Salton Sea.
Because there is no outlet to the ocean, these salts and minerals are concentrated by evaporation. 68,000 acre feet was lost annually by seepage from the All-American Canal from the point where the canal crosses the great Algodones Dune Field. About 90% of this seepage entered Mexico. At first this seepage caused widespread flooding, but Mexicali Valley residents and businesses built drainage and pumping systems to recover the seepage. Mexicali Valley agriculture became reliant upon this seepage for irrigation; as water use increased in both rural and urban areas, this seepage became an issue of concern. The All-American Canal Lining Project, a part of California's Colorado River Water Use Plan, lined 37 kilometers of the canal to prevent seepage. In 2006, a Mexicali business and civic organization and two California environmental non-profits challenged the lining project in US federal court on the basis that it violated the water rights of Mexican water users and violated US environmental statutes due to the seepage's effects on the nearby Andrade Mesa Wetlands.
A rider in the Tax Relief and Health Care Act of 2006 required the completion of the lining project and the lawsuit was rendered moot. The Imperial Irrigation District built a parallel canal along the designated section of the original canal, the water flow was rerouted into the new lined canal. Construction began in 2007 and was completed in 2009. Over 500 people have drowned in the All-American Canal since its completion due to deep, cold water, steep sides that make escape difficult, swift currents that can reach 5.45 mph. Many of those killed are undocumented migrants traveling across the U. S.-Mexico border. Deaths peaked at 31 in 1998 after increased border security measures in San Diego pushed undocumented migrants to cross the border in other areas. In 2011 the Imperial Irrigation District began installing lines with lifesaving buoys across the canal in 105 locations, despite debates about such safety measures encouraging illegal migration. Bilingual signs reading "Warning: Dangerous Water" were installed in 1,414 locations along the canal.
These safety projects cost $1.1 million. All-American Canal Bridge Brock Reservoir California Development Com
Wyoming is a state in the mountain region of the western United States. The state is the 10th largest by area, the least populous, the second most sparsely populated state in the country. Wyoming is bordered on the north by Montana, on the east by South Dakota and Nebraska, on the south by Colorado, on the southwest by Utah, on the west by Idaho and Montana; the state population was estimated at 577,737 in 2018, less than 31 of the most populous U. S. cities including Denver in neighboring Colorado. Cheyenne is the state capital and the most populous city, with an estimated population of 63,624 in 2017; the western two-thirds of the state is covered by the mountain ranges and rangelands of the Rocky Mountains, while the eastern third of the state is high elevation prairie called the High Plains. Half of the land in Wyoming is owned by the U. S. government, leading Wyoming to rank sixth by area and fifth by proportion of a state's land owned by the federal government. Federal lands include two national parks—Grand Teton and Yellowstone—two national recreation areas, two national monuments, several national forests, historic sites, fish hatcheries, wildlife refuges.
Original inhabitants of the region include the Crow, Arapaho and Shoshone. Southwestern Wyoming was in the Spanish Empire and Mexican territory until it was ceded to the United States in 1848 at the end of the Mexican–American War; the region acquired the name Wyoming when a bill was introduced to the U. S. Congress in 1865 to provide a "temporary government for the territory of Wyoming"; the name was used earlier for the Wyoming Valley in Pennsylvania, is derived from the Munsee word xwé:wamənk, meaning "at the big river flat". The main drivers of Wyoming's economy are mineral extraction—mostly coal, natural gas, trona—and tourism. Agricultural commodities include livestock, sugar beets and wool; the climate is semi-arid and continental and windier than the rest of the U. S. with greater temperature extremes. Wyoming has been a politically conservative state since the 1950s, with the Republican Party candidate winning every presidential election except 1964. Wyoming's climate is semi-arid and continental, is drier and windier in comparison to most of the United States with greater temperature extremes.
Much of this is due to the topography of the state. Summers in Wyoming are warm with July high temperatures averaging between 85 and 95 °F in most of the state. With increasing elevation, this average drops with locations above 9,000 feet averaging around 70 °F. Summer nights throughout the state are characterized by a rapid cooldown with the hottest locations averaging in the 50–60 °F range at night. In most of the state, most of the precipitation tends to fall in early summer. Winters are cold, but are variable with periods of sometimes extreme cold interspersed between mild periods, with Chinook winds providing unusually warm temperatures in some locations. Wyoming is a dry state with much of the land receiving less than 10 inches of rainfall per year. Precipitation depends on elevation with lower areas in the Big Horn Basin averaging 5–8 inches; the lower areas in the North and on the eastern plains average around 10–12 inches, making the climate there semi-arid. Some mountain areas do receive a good amount of precipitation, 20 inches or more, much of it as snow, sometimes 200 inches or more annually.
The state's highest recorded temperature is 114 °F at Basin on July 12, 1900 and the lowest recorded temperature is −66 °F at Riverside on February 9, 1933. The number of thunderstorm days vary across the state with the southeastern plains of the state having the most days of thunderstorm activity. Thunderstorm activity in the state is highest during early summer; the southeastern corner of the state is the most vulnerable part of the state to tornado activity. Moving away from that point and westwards, the incidence of tornadoes drops with the west part of the state showing little vulnerability. Tornadoes, where they occur, tend to be small and brief, unlike some of those that occur farther east; as specified in the designating legislation for the Territory of Wyoming, Wyoming's borders are lines of latitude 41°N and 45°N, longitude 104°3'W and 111°3'W, making the shape of the state a latitude-longitude quadrangle. Wyoming is one of only three states to have borders along only straight latitudinal and longitudinal lines, rather than being defined by natural landmarks.
Due to surveying inaccuracies during the 19th century, Wyoming's legal border deviates from the true latitude and longitude lines by up to half of a mile in some spots in the mountainous region along the 45th parallel. Wyoming is bordered on the north by Montana, on the east by South Dakota and Nebraska, on the south by Colorado, on the southwest by Utah, on the west by Idaho, it is the tenth largest state in the United States in total area, containing 97,814 square miles and is made up of 23 counties. From the north border to the south border it is 276 miles; the Great Plains meet the Rocky Mountains in Wyoming. The state is a great plateau broken by many mountain ranges. Surface elevations range from the summit of Gannett Peak in the Wind River Mountain Range, at 13,804 feet, to the Belle Fourche River val
The Sonoran Desert is a North American desert which covers large parts of the Southwestern United States in Arizona and California and of Northwestern Mexico in Sonora, Baja California, Baja California Sur. It is the hottest desert in Mexico, it has an area of 260,000 square kilometers. The western portion of the United States–Mexico border passes through the Sonoran Desert. In phytogeography, the Sonoran Desert is within the Sonoran Floristic Province of the Madrean Region in southwestern North America, part of the Holarctic Kingdom of the northern Western Hemisphere; the desert contains a variety of unique and endemic plants and animals, such as the saguaro and organ pipe cactus. The Sonoran desert wraps around the northern end of the Gulf of California, from Baja California Sur, north through much of Baja California, excluding the central northwest mountains and Pacific west coast, through southeastern California and southwestern and southern Arizona to western and central parts of Sonora.
It is bounded on the west by the Peninsular Ranges, which separate it from the California chaparral and woodlands and Baja California Desert ecoregions of the Pacific slope. To the north in California and northwest Arizona, the Sonoran Desert transitions to the colder-winter, higher-elevation Mojave, Great Basin, Colorado Plateau deserts. To the east and southeast, the deserts transition to the coniferous Arizona Mountains forests and Sierra Madre and Sierra Madre Occidental pine–oak forests at higher elevations. To the south the Sonoran–Sinaloan transition subtropical dry forest is the transition zone from the Sonoran Desert to the tropical dry forests of the Mexican state of Sinaloa; the desert's sub-regions include the Colorado Desert of southeastern California. In the 1957 publication Vegetation of the Sonoran Desert, Forrest Shreve divided the Sonoran Desert into seven regions according to characteristic vegetation: Lower Colorado Valley, Arizona Upland, Plains of Sonora, Foothills of Sonora, Central Gulf Coast, Vizcaíno Region, Magdalena Region.
Many ecologists now consider Shreve's Vizcaíno and Magdalena regions, which lie on the western side of the Baja California Peninsula, to be a separate ecoregion, the Baja California Desert. Within the southern Sonoran Desert in Mexico is found the Gran Desierto de Altar, with the Reserva de la Biosfera el Pinacate y Gran Desierto de Altar, extending 2,000 square kilometers of desert and mountainous regions; the Pinacate National Park includes the only active erg dune region in North America. The nearest city to the Reserva de la Biosfera el Pinacate y Gran Desierto de Altar is Puerto Peñasco in the state of Sonora, Mexico. Sub-regionsSonoran Desert sub-regions include: Colorado Desert Gran Desierto de Altar Lechuguilla Desert Tonopah Desert Yuha Desert Yuma Desert The Sonoran Desert includes 60 mammal species, 350 bird species, 20 amphibian species, over 100 reptile species, 30 native fish species, over 1000 native bee species, more than 2,000 native plant species; the Sonoran Desert area southeast of Tucson and near the Mexican border is vital habitat for the only population of jaguars living within the United States.
The Colorado River Delta was once an ecological hotspot within the Sonoran desert, fueled by the flow of fresh water through the Colorado river in this otherwise dry area, but the delta has been reduced in extent due to the damming and use of the river upstream. Many plants not only thrive in the harsh conditions of the Sonoran Desert. Many have evolved to have specialized adaptations to the desert climate; the Sonoran Desert's biseasonal rainfall pattern results in more plant species than any other desert in the world. The Sonoran Desert includes plant genera and species from the agave family, palm family, cactus family, legume family, numerous others; the Sonoran is the only place in the world. Cholla, hedgehog, prickly pear, nightblooming cereus, organ pipe are other taxa of cacti found here. Cactus provides food and homes to many desert mammals and birds, with showy flowers in reds, pinks and whites, blooming most from late March through June, depending on the species and seasonal temperatures.
Creosote bush and bur sage dominate valley floors. Indigo bush and Mormon tea are other shrubs. Wildflowers of the Sonoran Desert include desert sand verbena, desert sunflower, evening primroses. Ascending from the valley up bajadas, various subtrees such as velvet mesquite, palo verde, desert ironwood, desert willow, crucifixion thorn are common, as well as multi-stemmed ocotillo. Shrubs found at higher elevations include whitethorn acacia, fairy duster, jojoba. In the desert subdivisions found on Baja California, cardon cactus, elephant tree, boojum tree occur; the California fan palm is found in the Colorado Desert section of the Sonoran Desert, the only native palm in California, among many other introduced Arecac
Horseshoe Bend (Arizona)
Horseshoe Bend is a horseshoe-shaped incised meander of the Colorado River located near the town of Page, Arizona, in the United States. Horseshoe Bend is located 5 miles downstream from the Glen Canyon Dam and Lake Powell within Glen Canyon National Recreation Area, about 4 miles southwest of Page, it is accessible via hiking a 1.5-mile round trip from U. S. Route 89. Horseshoe Bend can be viewed from the steep cliff above; the overlook is 4,200 feet above sea level, the Colorado River is at 3,200 feet above sea level, making it a 1,000-foot drop. The rock walls of Horseshoe Bend contain hematite, platinum and other minerals. By 2018 references to the location on social media had caused the number of visitors to increase significantly. Official website
Sonora Estado Libre y Soberano de Sonora, is one of 31 states that, with Mexico City, comprise the 32 federal entities of United Mexican States. It is divided into 72 municipalities. Sonora is bordered by the states of Chihuahua to the east, Baja California to the northwest and Sinaloa to the south. To the north, it shares the U. S.–Mexico border with the states of Arizona and New Mexico, on the west has a significant share of the coastline of the Gulf of California. Sonora's natural geography is divided into three parts: the Sierra Madre Occidental in the east of the state, it is arid or semiarid deserts and grasslands, with only the highest elevations having sufficient rainfall to support other types of vegetation. Sonora is home to eight indigenous peoples, including the Mayo, the O’odham, the Yaqui, Seri, it has been economically important for its agriculture and mining since the colonial period, for its status as a border state since the Mexican–American War. With the Gadsden Purchase, Sonora lost more than a quarter of its territory.
From the 20th century to the present, industry and agribusiness have dominated the economy, attracting migration from other parts of Mexico. Several theories exist as to the origin of the name "Sonora". One theory states that the name was derived from Nuestra Señora, the name given to the territory when Diego de Guzmán crossed the Yaqui River on the day of Nuestra Señora del Rosario, which falls on 7 October with the pronunciation changing because none of the indigenous languages of the area have the ñ sound. Another theory states that Álvar Núñez Cabeza de Vaca and his companions, who had wrecked off the Florida coast and made their way across the continent, were forced to cross the arid state from north to south, carrying an image of Nuestra Señora de las Angustias on a cloth, they encountered the Opata, who could not pronounce Señora, instead saying Sonora. A third theory, written by Father Cristóbal de Cañas in 1730, states that the name comes from the word for a natural water well, which the Spaniards modified to "Sonora".
The first record of the name Sonora comes from explorer Francisco Vásquez de Coronado, who passed through the state in 1540 and called part of the area the Valle de la Sonora. Francisco de Ibarra traveled through the area in 1567 and referred to the Valles de Señora; the literal meaning of "sonora" in Spanish is "sonorous" or "loud." Evidence of human existence in the state dates back over 10,000 years, with some of the best-known remains at the San Dieguito Complex in the El Pinacate Desert. The first humans were nomadic hunter gatherers who used tools made from stones and wood. During much of the prehistoric period, the environmental conditions were less severe than they are today, with similar but more dense vegetation spread over a wider area; the oldest Clovis culture site in North America is believed to be El Fin del Mundo in northwestern Sonora. It was discovered during a 2007 survey, it features occupation dating around 13,390 calibrated years BP. In 2011, remains of Gomphothere were found.
Agriculture first appeared around 400 200 CE in the river valleys. Remains of ceramics have been found dating from 750 CE with diversification from 800 and 1300 CE Between 1100 and 1350, the region had complex small villages with well-developed trade networks; the lowland central coast, seems never to have adopted agriculture. Because Sonora and much of the northwest does not share many of the cultural traits of that area, it is not considered part of Mesoamerica. Though evidence exists of trade between the peoples of Sonora and Mesoamerica, Guasave in Sinaloa is the most north-westerly point considered Mesoamerican. Three archaeological cultures developed in the low, flat areas of the state near the coast: the Trincheras tradition, the Huatabampo tradition, the Central Coast tradition; the Trincheras tradition is dated to between 750 and 1450 CE and known from sites in the Altar and Concepción valleys, but its range extended from the Gulf of California into northern Sonora. The tradition is named after trenches found in a number of sites, the best known of, the Cerro de Trincheras.
The Huatabampo tradition is centered south of the Trincheras along the coast, with sites along extinct lagoons and river valleys. This tradition has a distinctive ceramic complex. Huatabampo culture shows similarities with the Chametla to the Hohokam to the north; this ended around 1000 CE. Unlike the other two traditions, the Central Coast remained a hunter-gatherer culture, as the area lacks the resources for agriculture; the higher elevations of the state were dominated by the Casas Grandes and Río Sonora tradition. The Río Sonora culture is located in central Sonora from the border area to modern Sinaloa. A beginning date for this culture has not been determined but it disappeared by the early 14th century; the Casas Grandes tradition in Sonora was an extension of the Río Sonora tradition based in the modern state of Chihuahua, which exterted its influence down to parts of the Sonoran coast. Climatic changes in the middle of the 15th century resulted in the increased desertification of northwest Mexico in general.
This is the probable cause for the drastic decrease in the number and size of settlements starting around this time. The peoples that remained in the area reverted to a less complex social organiz