The California Gold Rush of 1848-1855 transformed the region from a sparsely populated Mexican territory to a booming American state. Sparked by James Marshall's discovery at Sutter's Mill, the rush attracted hundreds of thousands of fortune seekers, rapidly increasing California's population and economic importance. This period saw the rise of mining towns, the growth of San Francisco, and the development of infrastructure. It also led to environmental damage, conflicts with Native Americans, and ethnic tensions. The gold rush ultimately accelerated California's path to statehood in 1850.