Copper extraction refers to the methods used to obtaining copper from its ores. The conversion of copper consists of a series of electrochemical processes. Methods have evolved and vary with country depending on the ore source, local environmental regulations, other factors; as in all mining operations, the ore must be beneficiated. The processing techniques depend on the nature of the ore. If the ore is sulfide copper minerals, the ore is crushed and ground to liberate the valuable minerals from the waste minerals, it is concentrated using mineral flotation. The concentrate is then sold to distant smelters, although some large mines have smelters located nearby; such colocation of mines and smelters was more typical in the 19th and early 20th centuries, when smaller smelters could be economic. The sulfide concentrates are smelted in such furnaces as the Outokumpo or Inco flash furnace or the ISASMELT furnace to produce matte, which must be converted and refined to produce anode copper; the final refining process is electrolysis.
For economic and environmental reasons, many of the byproducts of extraction are reclaimed. Sulfur dioxide gas, for example, is captured and turned into sulfuric acid — which can be used in the extraction process or sold for such purposes as fertiliser manufacture. Oxidised copper ores can be treated by hydrometallurgical extraction; the earliest evidence of cold-hammering of native copper comes from the excavation at Çaÿonü Tepesi in eastern Anatolia, which dates between 7200 to 6600 BCE. Among the various items considered to be votive or amulets there was one that looked like a fishhook and one like an awl. Another find, at Shanidar Cave in Mergasur, contained copper beads, dates to 8,700 BCE; the world's oldest known copper mine, as opposed to usage of surface deposits, is at Timna Valley, since the fourth millennium BC, with smelting and surface deposit usage since the sixth to fifth millennium. Pločnik archaeological site in southeastern Europe contains the oldest securely dated evidence of copper making at high temperature, from 5,000 BCE.
The find in June 2010 extends for additional 500 years the earlier record of copper smelting from Rudna Glava, dated to 5th millennium BCE. Copper smelting technology gave rise to the Copper Age, aka Chalcolithic Age, the Bronze Age; the Bronze Age would not have been possible without humans developing smelting technology. Most copper ores contain only a small percentage of copper metal bound up within valuable ore minerals, with the remainder of the ore being unwanted rock or gangue minerals silicate minerals or oxide minerals for which there is no value. In some cases, tailings have been retreated to recover lost value as the technology for recovering copper has improved; the average grade of copper ores in the 21st century is below 0.6% copper, with a proportion of economic ore minerals being less than 2% of the total volume of the ore rock. A key objective in the metallurgical treatment of any ore is the separation of ore minerals from gangue minerals within the rock; the first stage of any process within a metallurgical treatment circuit is accurate grinding or comminution, where the rock is crushed to produce small particles consisting of individual mineral phases.
These particles are separated to remove gangue, thereafter followed by a process of physical liberation of the ore minerals from the rock. The process of liberation of copper ores depends upon whether they are sulfide ores. Subsequent steps depend on the nature of the ore containing the copper. For oxide ores, a hydrometallurgical liberation process is undertaken, which uses the soluble nature of the ore minerals to the advantage of the metallurgical treatment plant. For sulfide ores, both secondary and primary, froth flotation is used to physically separate ore from gangue. For special native copper bearing ore bodies or sections of ore bodies rich in supergene native copper, this mineral can be recovered by a simple gravity circuit; the modern froth flotation process was independently invented the early 1900s in Australia by C. V Potter and around the same time by G. D. Delprat. All primary sulfide ores of copper sulfides, most concentrates of secondary copper sulfides, are subjected to smelting.
Some vat leach or pressure leach processes exist to solubilise chalcocite concentrates and produce copper cathode from the resulting leachate solution, but this is a minor part of the market. Carbonate concentrates are a minor product produced from copper cementation plants as the end-stage of a heap-leach operation; such carbonate concentrates can be treated by a solvent extraction and electrowinning plant or smelted. The copper ore is crushed and ground to a size such that an acceptably high degree of liberation has occurred between the copper sulfide ore minerals and the gangue minerals; the ore is wet, suspended in a slurry, mixed with xanthates or other reagents, which render the sulfide particles hydrophobic. Typical reagents include potassium ethylxanthate and sodium ethylxanthate, but dithiophosphates and dithiocarbamates are used; the treated ore is introduced to a water-filled aeration tank containing surfactant such as methylisobutyl carbinol. Air is forced through the slurry and the air bubbles attach to the hydrophobic copper sulfide particles, which are conducted to the surface, where they form a froth and are skimmed off.
These skimmings are subjected to a cleaner-scavenger cell to remove excess silicates and to remove other sulfide minerals that can deleteriousl
The Huntington Library, Art Collections and Botanical Gardens, colloquially known as The Huntington, is a collections-based educational and research institution established by Henry E. Huntington and located in San Marino, United States. In addition to the library, the institution houses an extensive art collection with a focus on 18th- and 19th-century European art and 17th- to mid-20th-century American art; the property includes 120 acres of specialized botanical landscaped gardens, most notably the "Japanese Garden", the "Desert Garden", the "Chinese Garden". As a landowner, Henry Edwards Huntington played a major role in the growth of Southern California. Huntington was born in 1850, in Oneonta, New York, was the nephew and heir of Collis P. Huntington, one of the famous "Big Four" railroad tycoons of 19th century California history. In 1892, Huntington relocated to San Francisco with his first wife, Mary Alice Prentice, as well as their four children, he divorced Mary Alice Prentice in 1906.
He purchased a property of more than 500 acres, known as the "San Marino Ranch" and went on to purchase other large tracts of land in the Pasadena and Los Angeles areas of Los Angeles County for urban and suburban development. As president of the Pacific Electric Railway Company, the regional streetcar and public transit system for the Los Angeles metropolitan area and southern California and of the Los Angeles Railway Company, he spearheaded urban and regional transportation efforts to link together far-flung communities, supporting growth of those communities as well as promoting commerce and tourism, he was one of the founders of the City of San Marino, incorporated in 1913. Huntington's interest in art was influenced in large part by his second wife, Arabella Huntington, with art experts to guide him, he benefited from a post-World War I European market, "ready to sell anything". Before his death in 1927, Huntington amassed "far and away the greatest group of 18th-century British portraits assembled by any one man".
In accordance with Huntington's will, the collection worth $50 million, was opened to the public in 1928. On October 17, 1985, a fire erupted in an elevator shaft of the Huntington Art Gallery and destroyed Sir Joshua Reynolds's 1777 portrait of Mrs. Edwin Lascelles. After a year-long, $1 million refurbishing project, the Huntington Gallery reopened in 1986, with its artworks cleaned of soot and stains. Most of the funds for the cleanup and refurbishing of the Georgian mansion and its artworks came from donations from the Michael J. Connell Foundation and individuals. Both the Federal art-supporting establishment of the National Endowment for the Arts and the National Endowment for the Humanities gave emergency grants, the former of $17,500 to "support conservation and other related costs resulting from a serious fire at the Gallery of Art", the latter of $30,000 to "support the restoration of several fire-damaged works of art that depict the story of Western culture." The library building was designed in 1920, by the southern California architect Myron Hunt in the Mediterranean Revival style.
Hunt's previous commissions for Mr. and Mrs. Huntington included the Huntington's residence in San Marino in 1909, the Huntington Hotel in 1914; the library contains a substantial collection of rare books and manuscripts, concentrated in the fields of British and American history, literature and the history of science. Spanning from the 11th century to the present, the library's holdings contain 7 million items, over 400,000 rare books, over a million photographs and other ephemera. Highlights include one of eleven vellum copies of the Gutenberg Bible known to exist, the Ellesmere manuscript of Chaucer, letters and manuscripts by George Washington, Thomas Jefferson, Benjamin Franklin, Abraham Lincoln, it is the only library in the world with the first two quartos of Hamlet. The Library's Main Exhibition Hall showcases some of the most outstanding rare books and manuscripts in the collection, while the West Hall of the Library hosts rotating exhibitions; the Dibner Hall of the History of Science is a permanent exhibition on the history of science with a focus on astronomy, natural history and light.
With the 2006 acquisition of the Burndy Library, a collection of nearly 60,000 items, the Huntington became one of the top institutions in the world for the study of the history of science and technology. Use of the collection for research is restricted to qualified scholars requiring a doctoral degree or at least candidacy for the PhD, two letters of recommendation from known scholars. Through a rigorous peer-review program, the institution awards 150 grants to scholars in the fields of history, literature and the history of science; the Huntington hosts numerous scholarly events, lectures and workshops. In September 1991, then-director William A. Moffett announced that the library's photographic archive of the Dead Sea Scrolls would
Claremont McKenna College
Claremont McKenna College is a coeducational, private liberal arts college in Claremont, California. It has a curricular emphasis on economics, international relations and public affairs. CMC is a member of the Claremont Colleges consortium. Founded as a men's college in 1946, CMC became coeducational in 1976, its campus is located 35 miles east of Downtown Los Angeles. The college focuses on undergraduate education, but in 2007 it established the Robert Day School of Economics and Finance, which offers a master's program in finance. CMC is known for its conservative political orientation relative to comparable liberal arts colleges; as of 2016, there are 1,344 undergraduate students and postgraduate students. Claremont McKenna College was founded as Claremont Men's College in September 1946 with a founding class of 86 students and seven faculty. Many of its first students were war veterans of World War II attending college on the G. I. Bill. Claremont Men’s College was the third Claremont College, following Pomona College and Scripps College.
CMC founded with the mission to foster leadership in its students in the fields of government and international affairs. The college's motto is "Crescit cum commercio civitas", or "Civilization prospers with commerce". Following a national trend toward coeducation among colleges such as Yale, Williams and Dartmouth, Claremont Men's College faced compelling arguments to admit women in the 1970s. With support from students represented by the Associated Students of Claremont's Men College, the trustees of the college voted to admit women to CMC with a two-thirds vote. A year in 1976 Claremont Men's College admitted their first women to their freshman class; the President of Claremont Men's College during this transition Jack Stark would say the admission of women was the college’s most important moment. The women of the earliest classes of CMC are known as "Pioneers" and graduated with degrees that still bore the "Claremont's Mens College" moniker, it wasn't until 1981 that the college was renamed to Claremont McKenna College was renamed after Donald McKenna, a founding trustee.
In November 1989, a father of a CMC student hired a stripper to perform in the college's dining hall, sparking protests among some students. Then-president Jack Stark told the New York Times he did not wish to comment on "whether was or was not degrading to women". On the evening of March 9, 2004, visiting Assistant Professor of Psychology Kerri Dunn reported that her car had been vandalized and painted with racist and anti-semitic slurs. In response, there was a series of demonstrations, candlelight vigils and community meetings; the investigation by the City of Claremont's police department and the FBI revealed that Dunn had slashed her own tires and applied the insulting phrases to her own vehicle. She was found guilty of filing attempted insurance fraud, she was sentenced to one year in prison and ordered to pay a fine of $19,000 in restitution. On September 27, 2007, the college announced a $200 million gift from alumnus and trustee Robert Addison Day to create the "Robert Day Scholars Program" and a master's program in finance.
CMC literature professor Robert Faggen sent a letter signed by several other literature professors to CMC president Pamela Gann, saying they were concerned that the gift will "distort the college into a single focus trade school."On January 30, 2012, President Gann revealed that a "high-ranking admissions official," identified as the school's former dean of admissions, Richard C. Vos, had been inflating SAT scores reported to the U. S. News & World Report by 10-20 points over the previous six years. A 2013 Time article opined that "such a small differential could not have affected U. S. News & World Report rankings". A report commissioned by the college claimed to have found no evidence that these misrepresentations were made to inflate the school's rankings; the controversy prompted Forbes to omit CMC from its annual rankings in 2013. In November 2015, the college's dean of students resigned after students protested what they called a lack of institutional resources for marginalized students.
These protests followed and were associated with the 2015 University of Missouri protests. On April 6, 2017, a group of 300 student protesters blockaded the Marian Miner Cook Athenaeum in an attempt to shut down a speech by conservative pundit Heather Mac Donald; the college livestreamed the talk. The college disciplined seven of its students who participated in the blockade, including suspending two for a semester and three for a full year. CMC is chartered as a private, non-profit organization and is a member of the seven-institution Claremont Colleges consortium. Students can take classes at any of the member colleges, the colleges share libraries, student health, a bookstore, athletic facilities, various student services; the appointed, 40-voting-member board of trustees elects a president to serve as chief executive officer of the college. Hiram Chodosh is CMC's fifth president; the president has an executive cabinet of 9 vice presidents, including a VP of Students Affairs and VP of Academic Affairs.
George C. S. Benson, founding president Howard R. Neville Jack L. Stark Pamela Gann Hiram Chodosh In 2018, Forbes ranked Claremont McKenna as the 26th-best college in the nation and the 7th-best liberal arts college
Time is an American weekly news magazine and news website published in New York City. It was founded in 1923 and run by Henry Luce. A European edition is published in London and covers the Middle East, and, since 2003, Latin America. An Asian edition is based in Hong Kong; the South Pacific edition, which covers Australia, New Zealand, the Pacific Islands, is based in Sydney. In December 2008, Time discontinued publishing a Canadian advertiser edition. Time has the world's largest circulation for a weekly news magazine; the print edition has a readership of 26 million. In mid-2012, its circulation was over three million, which had lowered to two million by late 2017. Richard Stengel was the managing editor from May 2006 to October 2013, when he joined the U. S. State Department. Nancy Gibbs was the managing editor from September 2013 until September 2017, she was succeeded by Edward Felsenthal, Time's digital editor. Time magazine was created in 1923 by Briton Hadden and Henry Luce, making it the first weekly news magazine in the United States.
The two had worked together as chairman and managing editor of the Yale Daily News. They first called the proposed magazine Facts, they wanted to emphasize brevity. They changed the name to Time and used the slogan "Take Time–It's Brief". Hadden was liked to tease Luce, he saw Time as important, but fun, which accounted for its heavy coverage of celebrities, the entertainment industry, pop culture—criticized as too light for serious news. It set out to tell the news through people, for many decades, the magazine's cover depicted a single person. More Time has incorporated "People of the Year" issues which grew in popularity over the years. Notable mentions of them were Steve Jobs, etc.. The first issue of Time was published on March 3, 1923, featuring Joseph G. Cannon, the retired Speaker of the House of Representatives, on its cover. 1, including all of the articles and advertisements contained in the original, was included with copies of the February 28, 1938 issue as a commemoration of the magazine's 15th anniversary.
The cover price was 15¢ On Hadden's death in 1929, Luce became the dominant man at Time and a major figure in the history of 20th-century media. According to Time Inc.: The Intimate History of a Publishing Enterprise 1972–2004 by Robert Elson, "Roy Edward Larsen was to play a role second only to Luce's in the development of Time Inc". In his book, The March of Time, 1935–1951, Raymond Fielding noted that Larsen was "originally circulation manager and general manager of Time publisher of Life, for many years president of Time Inc. and in the long history of the corporation the most influential and important figure after Luce". Around the time they were raising $100,000 from wealthy Yale alumni such as Henry P. Davison, partner of J. P. Morgan & Co. publicity man Martin Egan and J. P. Morgan & Co. banker Dwight Morrow, Henry Luce, Briton Hadden hired Larsen in 1922 – although Larsen was a Harvard graduate and Luce and Hadden were Yale graduates. After Hadden died in 1929, Larsen purchased 550 shares of Time Inc. using money he obtained from selling RKO stock which he had inherited from his father, the head of the Benjamin Franklin Keith theatre chain in New England.
However, after Briton Hadden's death, the largest Time, Inc. stockholder was Henry Luce, who ruled the media conglomerate in an autocratic fashion, "at his right hand was Larsen", Time's second-largest stockholder, according to Time Inc.: The Intimate History of a Publishing Enterprise 1923–1941. In 1929, Roy Larsen was named a Time Inc. director and vice president. J. P. Morgan retained a certain control through two directorates and a share of stocks, both over Time and Fortune. Other shareholders were the New York Trust Company; the Time Inc. stock owned by Luce at the time of his death was worth about $109 million, it had been yielding him a yearly dividend of more than $2.4 million, according to Curtis Prendergast's The World of Time Inc.: The Intimate History of a Changing Enterprise 1957–1983. The Larsen family's Time stock was worth around $80 million during the 1960s, Roy Larsen was both a Time Inc. director and the chairman of its executive committee serving as Time's vice chairman of the board until the middle of 1979.
According to the September 10, 1979, issue of The New York Times, "Mr. Larsen was the only employee in the company's history given an exemption from its policy of mandatory retirement at age 65." After Time magazine began publishing its weekly issues in March 1923, Roy Larsen was able to increase its circulation by using U. S. radio and movie theaters around the world. It promoted both Time magazine and U. S. political and corporate interests. According to The March of Time, as early as 1924, Larsen had brought Time into the infant radio business with the broadcast of a 15-minute sustaining quiz show entitled Pop Question which survived until 1925". In 1928, Larsen "undertook the weekly broadcast of a 10-minute programme series of brief news summaries, drawn from current issues of Time magazine, broadcast over 33 stations throughout the United States". Larsen next arranged for a 30-minute radio program, The March of Time, to be broadcast over CBS, beginning on March 6, 1931; each week, the program presented a dramatisation of the week's news for its listeners, thus Time magazine itself was brought "to the attention of millions unaware
The Great Depression was a severe worldwide economic depression that took place during the 1930s, beginning in the United States. The timing of the Great Depression varied across nations, it was the longest and most widespread depression of the 20th century. In the 21st century, the Great Depression is used as an example of how intensely the world's economy can decline; the Great Depression started in the United States after a major fall in stock prices that began around September 4, 1929, became worldwide news with the stock market crash of October 29, 1929. Between 1929 and 1932, worldwide gross domestic product fell by an estimated 15%. By comparison, worldwide GDP fell by less than 1% from 2008 to 2009 during the Great Recession; some economies started to recover by the mid-1930s. However, in many countries the negative effects of the Great Depression lasted until the beginning of World War II; the Great Depression had devastating effects in countries both poor. Personal income, tax revenue and prices dropped, while international trade plunged by more than 50%.
Unemployment in the U. S. rose to 25% and in some countries rose as high as 33%. Cities around the world were hit hard those dependent on heavy industry. Construction was halted in many countries. Farming communities and rural areas suffered as crop prices fell by about 60%. Facing plummeting demand with few alternative sources of jobs, areas dependent on primary sector industries such as mining and logging suffered the most. Economic historians attribute the start of the Great Depression to the sudden devastating collapse of U. S. stock market prices on October 29, 1929, known as Black Tuesday. However, some dispute this conclusion and see the stock crash as a symptom, rather than a cause, of the Great Depression. After the Wall Street Crash of 1929 optimism persisted for some time. John D. Rockefeller said "These are days. In the 93 years of my life, depressions have gone. Prosperity has always returned and will again." The stock market turned upward in early 1930. This was still 30% below the peak of September 1929.
Together and business spent more in the first half of 1930 than in the corresponding period of the previous year. On the other hand, many of whom had suffered severe losses in the stock market the previous year, cut back their expenditures by 10%. In addition, beginning in the mid-1930s, a severe drought ravaged the agricultural heartland of the U. S. By mid-1930, interest rates had dropped to low levels, but expected deflation and the continuing reluctance of people to borrow meant that consumer spending and investment were depressed. By May 1930, automobile sales had declined to below the levels of 1928. Prices in general began to decline, although wages held steady in 1930. A deflationary spiral started in 1931. Farmers faced a worse outlook. At its peak, the Great Depression saw nearly 10% of all Great Plains farms change hands despite federal assistance; the decline in the U. S. economy was the factor. Frantic attempts to shore up the economies of individual nations through protectionist policies, such as the 1930 U.
S. Smoot–Hawley Tariff Act and retaliatory tariffs in other countries, exacerbated the collapse in global trade. By 1933, the economic decline had pushed world trade to one-third of its level just four years earlier. Change in economic indicators 1929–32 The two classical competing theories of the Great Depression are the Keynesian and the monetarist explanation. There are various heterodox theories that downplay or reject the explanations of the Keynesians and monetarists; the consensus among demand-driven theories is that a large-scale loss of confidence led to a sudden reduction in consumption and investment spending. Once panic and deflation set in, many people believed they could avoid further losses by keeping clear of the markets. Holding money became profitable as prices dropped lower and a given amount of money bought more goods, exacerbating the drop in demand. Monetarists believe that the Great Depression started as an ordinary recession, but the shrinking of the money supply exacerbated the economic situation, causing a recession to descend into the Great Depression.
Economists and economic historians are evenly split as to whether the traditional monetary explanation that monetary forces were the primary cause of the Great Depression is right, or the traditional Keynesian explanation that a fall in autonomous spending investment, is the primary explanation for the onset of the Great Depression. Today the controversy is of lesser importance since there is mainstream support for the debt deflation theory and the expectations hypothesis that building on the monetary explanation of Milton Friedman and Anna Schwartz add non-monetary explanations. There is consensus that the Federal Reserve System should have cut short the process of monetary deflation and banking collapse. If they had done this, the economic downturn would have been much shorter. British economist John Maynard Keynes argued in The General Theory of Employment and Money that lower aggregate expenditures in the economy contributed to a massive decline in income and to employment, well below the average.
In such a situation, the economy reached equilibrium at low levels of economic activity and high unemployment. Keynes' basic idea was simple
Los Angeles the City of Los Angeles and known by its initials L. A. is the most populous city in California, the second most populous city in the United States, after New York City, the third most populous city in North America. With an estimated population of four million, Los Angeles is the cultural and commercial center of Southern California; the city is known for its Mediterranean climate, ethnic diversity and the entertainment industry, its sprawling metropolis. Los Angeles is the largest city on the West Coast of North America. Los Angeles is in a large basin bounded by the Pacific Ocean on one side and by mountains as high as 10,000 feet on the other; the city proper, which covers about 469 square miles, is the seat of Los Angeles County, the most populated county in the country. Los Angeles is the principal city of the Los Angeles metropolitan area, the second largest in the United States after that of New York City, with a population of 13.1 million. It is part of the Los Angeles-Long Beach combined statistical area the nation's second most populous area with a 2015 estimated population of 18.7 million.
Los Angeles is one of the most substantial economic engines within the United States, with a diverse economy in a broad range of professional and cultural fields. Los Angeles is famous as the home of Hollywood, a major center of the world entertainment industry. A global city, it has been ranked 6th in the Global Cities Index and 9th in the Global Economic Power Index; the Los Angeles metropolitan area has a gross metropolitan product of $1.044 trillion, making it the third-largest in the world, after the Tokyo and New York metropolitan areas. Los Angeles hosted the 1932 and 1984 Summer Olympics and will host the event for a third time in 2028; the city hosted the Miss Universe pageant twice, in 1990 and 2006, was one of 9 American cities to host the 1994 FIFA men's soccer World Cup and one of 8 to host the 1999 FIFA women's soccer World Cup, hosting the final match for both tournaments. Home to the Chumash and Tongva, Los Angeles was claimed by Juan Rodríguez Cabrillo for Spain in 1542 along with the rest of what would become Alta California.
The city was founded on September 4, 1781, by Spanish governor Felipe de Neve. It became a part of Mexico in 1821 following the Mexican War of Independence. In 1848, at the end of the Mexican–American War, Los Angeles and the rest of California were purchased as part of the Treaty of Guadalupe Hidalgo, becoming part of the United States. Los Angeles was incorporated as a municipality on April 4, 1850, five months before California achieved statehood; the discovery of oil in the 1890s brought rapid growth to the city. The completion of the Los Angeles Aqueduct in 1913, delivering water from Eastern California assured the city's continued rapid growth; the Los Angeles coastal area was settled by the Chumash tribes. A Gabrieleño settlement in the area was called iyáangẚ, meaning "poison oak place". Maritime explorer Juan Rodríguez Cabrillo claimed the area of southern California for the Spanish Empire in 1542 while on an official military exploring expedition moving north along the Pacific coast from earlier colonizing bases of New Spain in Central and South America.
Gaspar de Portolà and Franciscan missionary Juan Crespí, reached the present site of Los Angeles on August 2, 1769. In 1771, Franciscan friar Junípero Serra directed the building of the Mission San Gabriel Arcángel, the first mission in the area. On September 4, 1781, a group of forty-four settlers known as "Los Pobladores" founded the pueblo they called El Pueblo de Nuestra Señora la Reina de los Ángeles,'The Town of Our Lady the Queen of the Angels'; the present-day city has the largest Roman Catholic Archdiocese in the United States. Two-thirds of the Mexican or settlers were mestizo or mulatto, a mixture of African and European ancestry; the settlement remained a small ranch town for decades, but by 1820, the population had increased to about 650 residents. Today, the pueblo is commemorated in the historic district of Los Angeles Pueblo Plaza and Olvera Street, the oldest part of Los Angeles. New Spain achieved its independence from the Spanish Empire in 1821, the pueblo continued as a part of Mexico.
During Mexican rule, Governor Pío Pico made Los Angeles Alta California's regional capital. Mexican rule ended during the Mexican–American War: Americans took control from the Californios after a series of battles, culminating with the signing of the Treaty of Cahuenga on January 13, 1847. Railroads arrived with the completion of the transcontinental Southern Pacific line to Los Angeles in 1876 and the Santa Fe Railroad in 1885. Petroleum was discovered in the city and surrounding area in 1892, by 1923, the discoveries had helped California become the country's largest oil producer, accounting for about one-quarter of the world's petroleum output. By 1900, the population had grown to more than 102,000; the completion of the Los Angeles Aqueduct in 1913, under the supervision of William Mulholland, assured the continued growth of the city. Due to clauses in the city's charter that prevented the City of Los Angeles from selling or providing water from the aqueduct to any area outside its borders, many adjacent city and communities became compelled to annex themselves into Los Angeles.
Los Angeles created the first municipal zoning ordinance in the United States. On September 14, 1908, the Los Angeles City Council promulgated residential and industrial land use zones; the new ordinance established three residential zones of a single type, where industrial uses were