In the history of the American frontier, John Sutter (1803-1880) looms large. A Swiss expatriate who attempted to create a personal empire in California's Sacramento Valley, he founded New Helvetia, a cosmopolitan settlement whose economy depended on Indian slaves and free laborers. New Helvetia drew overland immigrants to California in the 1840s and then--after gold was discovered by Sutter's employees--a flood of fortune seekers. Sutter was poised...