James Monroe's public career began with service in the Continental Army, including the campaign in which he was wounded at Trenton. After legal study and entry into Virginia politics, he served in the Continental Congress and the United States Senate. A diplomatic appointment to France in 1794 brought him into the contentious politics of the French Revolution and relations with the Washington administration. Service as Virginia governor added to his experience. With Robert Livingston he negotiated the Louisiana Purchase in 1803.

Monroe served as secretary of state under James Madison and, during the final phase of the War of 1812, also as secretary of war. Elected president in 1816, he sought to reduce partisan division and toured the country. The collapse of the Federalists encouraged the description Era of Good Feelings, but it concealed growing disputes over slavery, development and regional interests. He was reelected with almost no electoral opposition in 1820. The Panic of 1819 nevertheless exposed economic insecurity, and debates over banks, tariffs and federal spending continued throughout his administration.

The Missouri controversy demonstrated the limits of national harmony. Monroe signed the compromise admitting Missouri as a slave state and Maine as a free state while restricting slavery in much of the remaining Louisiana Purchase territory. It postponed rather than resolved the struggle over slavery's expansion. Monroe himself enslaved people and supported colonization, illustrating the racial limits of his vision of republican liberty. On internal improvements he favoured development but questioned whether the Constitution authorized particular forms of federal control without an amendment.

Foreign affairs brought lasting consequences. The Adams–Onís Treaty of 1819 secured Florida and defined a boundary with Spanish possessions to the west; military pressure and expansionist ambitions shaped the negotiations. In his 1823 annual message Monroe warned European powers against further colonization and interference in the Americas, while disclaiming intervention in Europe's existing conflicts. Developed with Secretary of State John Quincy Adams, these statements later became known as the Monroe Doctrine. Enforcement was limited. After leaving office in 1825, Monroe remained involved in Virginia affairs but faced debt and declining health. He died in 1831. His career advanced national expansion while leaving conflicts over slavery unresolved.