When did the California Gold Rush occur?

The California Gold Rush began in January 1848 with the discovery of gold at Sutter's Mill and reached its peak from 1849 to 1852, with the famous "Forty-Niners" of 1849 arriving in the largest single year wave. James W. Marshall discovered gold on January 24, 1848 in the tailrace of a sawmill on the American River at Coloma, California, while building the mill for landowner John Sutter. Marshall had been digging out the tailrace to deepen the channel, and gold flakes caught his eye in the morning light. Sutter tried to keep the discovery quiet to protect his agricultural empire, but the news leaked through workers and traders.

The Treaty of Guadalupe Hidalgo signed on February 2, 1848 transferred California from Mexico to the United States, just nine days after the discovery. Local migration began through the spring and summer of 1848. Sam Brannan, a Mormon merchant who owned a store at Sutter's Fort, walked the streets of San Francisco in May 1848 waving a vial of gold dust and shouting "Gold! Gold! Gold from the American River!" The local rush emptied San Francisco and other coastal towns of their men.

President James K. Polk's annual message to Congress on December 5, 1848 confirmed the discovery, and gold samples reached Washington in late November 1848. The news exploded across the eastern United States and around the world during the winter of 1848 to 1849. The migration of 1849, called the Forty-Niners, brought roughly 80,000 people to California in a single year by overland trail, around Cape Horn by sea, and across the Isthmus of Panama. Migration continued at high levels through the early 1850s.

Approximately 300,000 people had reached California by 1855, transforming a Mexican frontier with about 14,000 non-Native inhabitants in 1846 into an American state with 380,000 people in the 1860 census. The bulk of the easily accessible placer gold was extracted by 1855, although mining continued in industrial form for decades. The peak production years were 1852 to 1853, when annual output reached about 81 million dollars at contemporary prices. Estimates of total gold extracted from California from 1848 through 1855 range from 600 million to 1 billion dollars at contemporary prices, perhaps the equivalent of 25 to 35 billion dollars today.

The migration reshaped the population, economy, politics, and ecology of California and accelerated the admission of California as a free state on September 9, 1850 as part of the Compromise of 1850.