As an explorer, John Charles Fremont led five expeditions into the American West--two of them disastrous. He was also one of California's first two senators (1850), America's first Republican candidate for president (1856), a Civil War general, and the territorial governor of Arizona (1878-83). But his life was one of rash and rebellious conduct against authority. During the Mexican War he claimed to be the military governor of California, which resulted in a court-martial in 1848. At the outbreak of the Civil War he reentered the army as one of four major generals, outranking even Ulysses S. Grant. However, when he antagonized President Abraham Lincoln by issuing his own emancipation proclamation in advance of the president's, Lincoln relieved him of command. In this comprehensive biography, Andrew Rolle carefully examines the historical record with a psychobiographical approach that explores and explains the many irrationalities of Fremont's character.