A carpenter's discovery of gold flakes triggered a mass migration to California

In January 1848, carpenter James Marshall spotted gold flakes in the American River while building a sawmill for John Sutter. Word spread, and by 1849 some 300,000 people, nicknamed the forty-niners, had rushed to California from across the US and the world, founding San Francisco as a boomtown almost overnight. California's economy exploded so fast it skipped territorial status and became a state within two years, while most of the gold wealth went to merchants, not the miners.

— J. S. Holliday, The World Rushed In: The California Gold Rush Experience — 1981