Thomas Jefferson began public work as a Virginia lawyer and legislator, then became a delegate to the Continental Congress. In 1776 he drafted the principal text of the Declaration of Independence, revised by colleagues and Congress. As Virginia governor from 1779 to 1781, he faced wartime invasion and criticism of the state's defense. His subsequent reform work included the statute for religious freedom adopted in 1786.

Jefferson served as minister to France from 1785 to 1789 and became the first secretary of state under George Washington. Disagreement with Alexander Hamilton over finance, constitutional interpretation, and foreign policy helped produce an organized Republican opposition. After serving as vice president under John Adams, he won the disputed election of 1800 following House balloting that resolved an electoral tie with Aaron Burr.

As president from 1801 to 1809, Jefferson sought reduced federal expenditure and debt while exercising substantial executive authority. The Louisiana Purchase in 1803 greatly expanded United States territorial claims, and the Lewis and Clark expedition gathered information about the West. These developments also advanced settlement and pressure on Indigenous lands. His government fought the Barbary conflict and confronted British and French interference with shipping. The Embargo Act of 1807 damaged American commerce without compelling the European powers to change policy. He signed the law ending legal United States participation in the international slave trade from 1808, while domestic slavery continued.

After retirement Jefferson worked to establish the University of Virginia and pursued architecture, agriculture, correspondence, and writing. His Notes on the State of Virginia included scientific observations as well as racist claims. Evidence supports that he fathered children with the enslaved Sally Hemings, whose position precluded equal power or freedom within the relationship. He died in 1826. His career helped define republican institutions and religious liberty, but its assessment must retain the contradiction between universal rights and slavery. Territorial expansion, educational projects, and political leadership were supported by wealth and labor extracted from enslaved people. The influence of his words cannot erase these practices, just as their later use by people seeking equality exceeded the limits of the society he helped govern.