To: POKERSAM who wrote (834997 ) 2/7/2015 6:37:26 PM From: Mongo2116 Respond to of 1577122 The Treaty of 1848 expanded United States territory by one-third after the Mexican-American War . To settle the war, Mexico ceded all or parts of Arizona , California , Colorado , Kansas , New Mexico , Nevada , Oklahoma , Texas , Utah , and Wyoming to the United States. In September 1850, California became the 31st state of the United States. Many of the Mexicans who were native to what would become a state within the United States were experienced miners, and they had great success mining gold in California. [10] Their success aroused animosity by white prospectors, who intimidated Mexican miners with the threat of violence and committed violence against some. Between 1848 and 1860, European Americans lynched at least 163 Mexicans in California alone. [10] On July 5, 1851, a mob in Downieville, California , lynched a Mexican woman named Josefa Segovia . [11] She was accused of killing a white man who had attempted to assault her after breaking into her home. [12] The San Francisco Vigilance Movement has traditionally been portrayed as a positive response to government corruption and rampant crime. But, revisionist historians have argued that it created more lawlessness than it eliminated. It had a strongly nativist tinge. [13] [ page needed ] Its members initially targeted activities by the Irish and later mounted mob violence against Chinese immigrants and Mexicans . [13] In 1871, a mob rampaged through Old Chinatown in Los Angeles and killed at least 18 Chinese Americans, after a white businessman was inadvertently killed there in the crossfire of a tong battle within the Chinese community. Another well-documented episode in the history of the American West is the Johnson County War , a dispute in the 1890s over land use in Wyoming . Large-scale ranchers, with the complicity of local and federal Republican politicians, hired mercenaries and assassins to lynch the small ranchers, who were mostly Democrats . The latter were also their economic competitors, characterized by the large-scale ranchers as "cattle rustlers".[ citation needed ] Reconstruction (1865–1877)[ edit ]