In 1849, Representative Abraham Lincoln returned to Illinois, his political career all but finished. Yet within a decade, Lincoln would win the 1860 presidential election, and keep America together during its most perilous period. How did it happen? As Michael Gerhardt reveals, Lincoln drew from the wisdom of Henry Clay, Andrew Jackson, and Zachary Taylor, learning an astonishing range of skills. Without these mentors, Gerhardt suggests here, Lincoln would likely have remained a small-town lawyer—and the United States as we know it may not have survived.