The term "forty-niners" refers to the thousands of prospectors who flocked to California in 1849 during the California Gold Rush. They were drawn by the discovery of gold at Sutter's Mill in 1848, which sparked a massive migration. Many traveled long distances, often facing harsh conditions, in hopes of striking it rich. These individuals came from various backgrounds, including American settlers, immigrants from Europe, and even Chinese laborers. The influx of forty-niners significantly impacted California's population and economy, leading to its rapid growth and eventual statehood in 1850.