On January 24, 1848, James W. Marshall, a carpenter and sawmill operator, stumbled upon a small shiny material while overseeing the construction of Sutter’s Mill on the American River. Due to the speculation around the claims of gold, the Gold Rush did not begin until December of 1848 when President James Polk proclaimed to the public that there was, in fact, gold! These miners became known as the 49ers, while the Mexican and Chilean miners who had arrived by the summer of 1848 were known as the 48ers.