A chance discovery on January 24, 1848, profoundly shaped the destiny of California and the world. On this day, in a river valley that quickly became the town of Coloma, James W. Marshall found gold in the tailrace of a sawmill he was building for John Sutter. The discovery precipitated the largest gold rush in history, bringing an estimated 300,000 fortune-seekers from all over the world in just a few years. By 1849, Coloma mushroomed into a town of 10,000 people, most of them transient miners. Soon, the town became more permanent, with grand hotels, fine homes, and stout brick buildings. In...