Political map of North America & the Caribbean 11 February 1849 (California Gold Rush): Just days before the signing of the Treaty of Guadalupe Hidalgo, gold was discovered at Sutter's Mill in California. Despite attempts to keep the find secret, word spread across the country, reaching the East Coast by August. Over the following years some 300,000 people from all around the world traveled to California by land and sea (California Gold Rush) in the first of the great gold rushes of the 19th century.