January 24, 1848 Gold is discovered at Sutter's Mill James W. Marshall discovers gold at Sutter's Mill in Coloma, beginning the California Gold Rush. February 2, 1848 Treaty of Guadalupe Hidalgo is signed The treaty ending the Mexican-American War transfers California to the United States just days after the gold discovery. March 1848 News of the find begins spreading locally Rumors move through northern California and the nearby Pacific world as miners head toward the American River. August 1848 Eastern U.S. press confirms the discovery Public confirmation by President James K. Polk and newspapers turns a regional rush into a national one. December 1848 President Polk endorses the reports to Congress Polk's official message confirms that the California reports are true and accelerates migration to the goldfields. 1849 Forty-niners pour into California Large numbers of migrants from the United States and abroad enter California in search of fortune. 1849 San Francisco grows explosively The small port of San Francisco rapidly becomes the commercial hub of the gold-rush economy. 1849 Mining camps spread through the Sierra foothills Temporary camps and boomtowns appear across the foothills as prospectors stake claims along rivers and creeks. October 1849 California constitutional convention meets Delegates gather in Monterey to draft a state constitution as the Gold Rush drives rapid political change. September 9, 1850 California enters the Union California is admitted as a state as part of the Compromise of 1850, a transition accelerated by the Gold Rush. 1850 Foreign miners tax is enacted California imposes a tax aimed largely at foreign miners, reflecting discrimination and competition in the goldfields. c. 1851 Violence and dispossession intensify for Native Californians Gold-rush settlement and militia violence accelerate the destruction of Native communities across California. 1851 Gold output reaches a new high Annual gold production surges as industrializing methods and large migrant numbers transform extraction. 1852 Rush reaches its peak year The migration and output of the Gold Rush crest around 1852 before beginning a gradual decline. 1852 Chinese migration to the goldfields rises sharply Growing numbers of migrants from China become an important part of the diverse mining population. 1853 Hydraulic mining begins to spread More capital-intensive techniques increasingly replace simple placer mining in many districts. 1854 Sacramento and interior transport networks expand Roads, river traffic, and commercial services tie the mining districts more firmly to urban markets. 1855 Initial rush phase wanes By the mid-1850s, easy surface deposits are harder to find and many independent prospectors leave or change occupations. 1856 Mining becomes more corporate and mechanized Larger firms and better-capitalized operations increasingly dominate extraction after the first rush. 1859 Comstock Lode redirects western mining attention The discovery of the Comstock Lode in Nevada helps shift speculative energy away from California's first gold rush dist… 1884 Hydraulic mining is sharply curtailed by court ruling The Sawyer decision restricts debris-producing hydraulic mining, symbolizing the long environmental aftermath of the ru…