Thomas Jefferson served as the third president of the United States from March 4, 1801, to March 4, 1809. Jefferson assumed the office after defeating incumbent John Adams in the 1800 presidential election. The election was a political realignment in which the Democratic-Republican Party swept the Federalist Party out of power, ushering in a generation of Jeffersonian Republican dominance in American politics. After serving two terms, Jefferson was succeeded by Secretary of State James Madison, also of the Democratic-Republican Party.

Thomas Jefferson was an American statesman, diplomat, lawyer, architect, philosopher, and Founding Father who served as the third president of the United States from 1801 to 1809. He was the primary author of the Declaration of Independence. Following the American Revolutionary War and prior to becoming president in 1801, Jefferson was the nation's first U.S. secretary of state under George Washington and then the nation's second vice president under John Adams.