Sean A. Mirski tells the riveting story of how the United States became a regional hegemon in the century following the Civil War. By turns reluctant and ruthless, Americans squeezed their European rivals out of the hemisphere while landing forces on their neighbors' soil. Mirski reveals the surprising reasons behind this muscular foreign policy in a narrative full of twists, colorful characters, and original accounts of the palace coups and bloody interventions that turned the fledgling republic into a global superpower.