Military history of California California ( ) is a state located on the West Coast of the United States . It is the most populous U . S . state , home to 1 out of 8 Americans ( 38 million people ) , and is the third largest state by area ( after Alaska and Texas ) . California is bordered by Oregon to the north , Nevada to the east , Arizona to the southeast , and the Mexican State of Baja California to the south . It is home to the nation ' s second and fifth most populous census statistical areas ( Greater Los Angeles area and San Francisco Bay Area , respectively ) , and eight of the nation ' s 50 most populated cities ( Los Angeles , San Diego , San Jose , San Francisco , Fresno , Sacramento , Long Beach , and Oakland ) . The capital city is Sacramento . What is now California was first settled by various Native American tribes before being explored by a number of European expeditions throughout the 16th and 17th centuries . It was then claimed by the Spanish Empire as part of Alta California in the larger territory of New Spain . Alta California became a part of Mexico in 1821 following its successful war for independence , but would later be ceded to the United States in 1848 after the Mexican - American War . The western portion of Alta California was soon organized as the State of California , which was admitted as the 31st state on September 9 , 1850 . The California Gold Rush starting in 1848 led to dramatic social and demographic change , with large scale immigration from the U . S . and abroad and an accompanying economic boom . Geography . California is the 3rd largest state in the United States in area , after Alaska and Texas . In the middle of the state lies the California Central Valley , bounded by the coastal mountain ranges in the west , the Sierra Nevada to the east , the Cascade Range in the north and the Tehachapi Mountains in the south . The Central Valley is California ' s agricultural heartland . Divided in two by the Sacramento - San Joaquin River Delta , the northern portion , the Sacramento Valley serves as the watershed of the Sacramento River , while the southern portion , the San Joaquin Valley is the watershed for the San Joaquin River ; both areas derive their names from the rivers that transit them . With dredging , the Sacramento and the San Joaquin Rivers have remained sufficiently deep that several inland cities are seaport s . The Sacramento - San Joaquin River Delta serves as a critical water supply hub for the state . Water is routed through an extensive network of canals and pumps out of the delta , that traverse nearly the length of the state , including the Central Valley Project and the State Water Project . Water from the Delta provides drinking water for nearly 23 million people , almost two - thirds of the state ' s population , and provides water to farmers on the west side of the San Joaquin Valley . The Channel Islands are located off the southern coast . The Sierra Nevada ( Spanish for " snowy range " ) includes the highest peak in the contiguous 48 states , Mount Whitney , at . The range embraces Yosemite Valley , famous for its glacially carved domes , and Sequoia National Park , home to the giant sequoia trees , the largest living organisms on Earth , and the deep freshwater lake , Lake Tahoe , the largest lake in the state by volume . To the east of the Sierra Nevada are Owens Valley and Mono Lake , an essential migratory bird habitat . In the western part of the state is Clear Lake , the largest freshwater lake by area entirely in California . Though Lake Tahoe is larger , it is divided by the California / Nevada border . The Sierra Nevada falls to Arctic temperatures in winter and has several dozen small glaciers , including Palisade Glacier , the southernmost glacier in the United States . About 45 percent of the state ' s total surface area is covered by forests , and California ' s diversity of pine species is unmatched by any other state . California contains more forestland than any other state except Alaska . Many of the trees in the California White Mountains are the oldest in the world ; an individual Bristlecone pine has an age over 5 , 000 years . In the south is a large inland salt lake , the Salton Sea . The south - central desert is called the Mojave ; to the northeast of the Mojave lies Death Valley , which contains the lowest and hottest place in North America , the Badwater Basin at . The horizontal distance from the nadir of Death Valley to the summit of Mount Whitney is less than . Indeed , almost all of southeastern California is arid , hot desert , with routine extreme high temperatures during the summer . The southeastern border of California with Arizona is entirely formed by the Colorado River , from which the southern part of the state gets about half of its water . Along the California coast are several major metropolitan areas , including Greater Los Angeles Area , the San Francisco Bay Area , and the San Diego metropolitan area . As part of the Ring of Fire , California is subject to tsunamis , floods , droughts , Santa Ana winds , wildfires , landslides on steep terrain , and has several volcanoes . It sees numerous earthquakes due to several faults , in particular the San Andreas Fault . History . Settled by successive waves of arrivals during the last 10 , 000 years , California was one of the most culturally and linguistically diverse areas in pre - Columbian North America . Various estimates of the native population range from 100 , 000 to 300 , 000 , which was about one - third of all native Americans in what is now the United States . The Indigenous peoples of California included more than 70 distinct groups of Native Americans , ranging from large , settled populations living on the coast to groups in the interior . California groups also were diverse in their political organization with bands , tribes , villages , and on the resource - rich coasts , large chiefdoms , such as the Chumash , Pomo and Salinan . Trade , intermarriage and military alliances fostered many social and economic relationships among the diverse groups . The first European effort to explore the coast as far north as the Russian River was a Spanish sailing expedition , led by Portuguese captain Juan Rodríguez Cabrillo , in 1542 . Some 37 years later English explorer Francis Drake also explored and claimed an undefined portion of the California coast in 1579 . Spanish traders made unintended visits with the Manila Galleon s on their return trips from the Philippines beginning in 1565 . Sebastián Vizcaíno explored and mapped the coast of California in 1602 for New Spain . Finally , after the Portola expedition of 1769 - 70 , Spanish missionaries began setting up 21 California Missions on or near the coast of Alta ( Upper ) California , beginning in San Diego . During the same period , Spanish military forces built several forts ( " presidio s " ) and three small towns ( " pueblos " ) . Two of the pueblos grew into the cities of Los Angeles and San Jose . 19th century . In 1821 the Mexican War of Independence gave Mexico ( including California ) independence from Spain ; for the next 25 years , Alta California remained a remote northern province of the nation of Mexico . Cattle ranches , or " ranchos " , emerged as the dominant institutions of Mexican California . After Mexican independence from Spain , the chain of missions became the property of the Mexican government and were secularized by 1834 . The ranchos developed under ownership by Californios ( Spanish - speaking Californians ) who had received land grants , and traded cowhides and tallow with Boston merchants . Beginning in the 1820s , trappers and settlers from the U . S . and Canada began to arrive in Northern California . These new arrivals used the Siskiyou Trail , California Trail , Oregon Trail and Old Spanish Trail to cross the rugged mountains and harsh deserts surrounding California . In this period , Imperial Russia explored the California coast and established a trading post at Fort Ross . In between 1831 to 1836 , California experienced a series of revolts against Mexico ; this culminated in the 1836 California revolt lead by Juan Bautista Alvarado , which ended after Mexico appointed him governor of the department . The revolt , which had momentarily declared California an independent state , was successful with the assistance of American and British residents of California , including Isaac Graham ; after 1840 , 100 of those residents who did not have passports were arrested , leading to the Graham affair in 1840 . In 1846 settlers rebelled against Mexican rule during the Bear Flag Revolt . Afterwards , rebels raised the Bear Flag ( featuring a bear , a star , a red stripe and the words " California Republic " ) at Sonoma . The Republic ' s first and only president was William B . Ide , who played a pivotal role during the Bear Flag Revolt . The California Republic was short lived ; the same year marked the outbreak of the Mexican - American War ( 1846 – 1848 ) . When Commodore John D . Sloat of the United States Navy sailed into Monterey Bay and began the military occupation of California by the United States , Northern California capitulated in less than a month to the U . S . forces . After a series of defensive battles in Southern California , the Treaty of Cahuenga was signed by the Californios on January 13 , 1847 , securing American control in California . Following the Treaty of Guadalupe Hidalgo that ended the war , the region was divided between Mexico and the U . S . ; the western territory of Alta California , was to become the U . S . state of California , and Arizona , Nevada , Colorado and Utah became U . S . Territories , while the lower region of California , the Baja Peninsula , remained in the possession of Mexico . In 1846 the non - native population of California was estimated to be no more than 8 , 000 , plus about 100 , 000 Native Americans down from about 300 , 000 prior to Hispanic settlement in 1769 . After gold was discovered , the population burgeoned with U . S . citizens , Europeans , Chinese and other immigrants during the great California Gold Rush . By 1854 over 300 , 000 settlers had come . Between 1847 and 1870 , the population of San Francisco increased from 500 to 150 , 000 . On September 9 , 1850 , as part of the Compromise of 1850 , California was admitted to the United States undivided as a free state , denying the expansion of slavery to the Pacific Coast . California ' s native population precipitously declined , above all , from Eurasian diseases to which they had no natural immunity . Like in other states , the native inhabitants were forcefully removed from their lands by incoming miners , ranchers , and farmers . And despite the fact that California entered the union as a free state , the " loitering or orphaned Indians " were de facto enslaved by Mexican and Anglo - American masters under the 1853 " Act for the Government and Protection of Indians " . There were several massacres in which hundreds of indigenous people were killed . Between 1850 and 1860 , California paid around 1 . 5 million dollars ( some 250 , 000 of which was reimbursed by the federal government ) to hire militias whose purpose was to protect settlers from the indigenous populations . In subsequent decades , the native population was placed in reservations and rancherias , which were often very small and isolated and lacked adequate natural resources or funding from the government to sustain the populations living on them . As a result , the rise of California brought great hardship for the native inhabitants . Several scholars and Native American activists , including Benjamin Madley and Ed Castillo , have described the actions of the California government as a genocide . The seat of government for California under Spanish and later Mexican rule was located at Monterey from 1777 until 1845 . Pio Pico , last Mexican governor of Alta California , moved the capital to Los Angeles in 1845 . The United States consulate was also located in Monterey , under consul Thomas O . Larkin . In 1849 , the Constitutional Convention was first held in Monterey . Among the tasks was a decision on a location for the new state capital . The first legislative sessions were held in San Jose ( 1850 – 1851 ) . Subsequent locations included Vallejo ( 1852 – 1853 ) , and nearby Benicia ( 1853 – 1854 ) ; these locations eventually proved to be inadequate as well . The capital has been located in Sacramento since 1854 with only a short break in 1861 when legislative sessions were held in San Francisco due to flooding in Sacramento . Initially , travel between California and the rest of the continental U . S . was time consuming and dangerous . A more direct connection came in 1869 with the completion of the First Transcontinental Railroad through Donner Pass in the Sierra Nevada mountains . Once completed , hundreds of thousands of U . S . citizens came west , where new Californians were discovering that land in the state , if irrigated during the dry summer months , was extremely well suited to fruit cultivation and agriculture in general . Vast expanses of wheat , other cereal crops , vegetable crops , cotton , and nut and fruit trees were grown ( including oranges in Southern California ) , and the foundation was laid for the state ' s prodigious agricultural production in the Central Valley and elsewhere . 20th century . Migration to California accelerated during the early - 20th century with the completion of major transcontinental highways like the Lincoln Highway and Route 66 . In the period from 1900 to 1965 , the population grew from fewer than one million to become the most populous state in the Union . In 1940 , the Census Bureau reported California ' s population as 6 . 0 % Hispanic , 2 . 4 % Asian , and 89 . 5 % non - Hispanic white . The 1906 San Francisco earthquake and 1928 St . Francis Dam flood remain the deadliest in U . S history . In order to meet the population ' s needs , major engineering feats like the California and Los Angeles Aqueduct s ; the Oroville and Shasta Dam s ; and the Bay and Golden Gate Bridges were built across the state . The state government also adopted the California Master Plan for Higher Education in 1960 to develop a highly efficient system of public education . Meanwhile , attracted to the mild Mediterranean climate , cheap land , and the state ' s wide variety of geography , filmmakers established the studio system in Hollywood in the 1920s . California manufactured 8 . 7 percent of total United States military armaments produced during World War II , ranking third ( behind New York and Michigan ) among the 48 states . After World War II , California ' s economy greatly expanded due to strong aerospace and defense industries , whose size decreased following the end of the Cold War . Stanford University and its Dean of Engineering Frederick Terman began encouraging faculty and graduates to stay in California instead of leaving the state , and develop a high - tech region in the area now known as Silicon Valley . As a result of these efforts , California is currently regarded as a world center of the entertainment and music industries , of technology , engineering , and the aerospace industry , and as the U . S . center of agricultural production . Just before the " Dot Com Bust " California had the 5th largest economy in the world among nations . Armed forces . In California , , the U . S . Department of Defense had a total of 117 , 806 active duty servicemembers of which 88 , 370 were Sailors or Marines , 18 , 339 were Airmen , and 11 , 097 were Soldiers , with 61 , 365 Department of Defense civilian employees . Additionally , there were a total of 57 , 792 Reservists and Guardsman in California . In 2010 , Los Angeles County was the largest origin of military recruits in the United States by county , with 1 , 437 individuals enlisting in the military . However , as of 2002 , Californians were relatively under - represented in the military as a proportion to its population . In 2000 , California , had 2 , 569 , 340 veterans of U . S . military service : 504 , 010 served in World War II , 301 , 034 in the Korean War , 754 , 682 during the Vietnam War , and 278 , 003 during 1990 – 2000 ( including the Persian Gulf War ) . , there were 1 , 942 , 775 veterans living in California , of which 1 , 457 , 875 served during a period of armed conflict , and just over four thousand served before World War II ( the largest population of this group of any state ) . California ' s military forces consist of the Army and Air National Guard , the naval and state military reserve ( militia ) , and the California Cadet Corps .