Sutter's Mill was a famous old wooden water-powered grist mill (a type of mill that grinds grain into flour and other food products) located along the American River in what is now the state of California in the United States. It is important because in 1848, a man named James Marshall discovered gold near the mill, leading to what became known as the California Gold Rush. This changed the history of the state and the United States, as thousands of people travelled to California in search of wealth.