Thomas Jefferson (April 13, 1743 – July 4, 1826) was the third President of the United States (1801–1809) and the principal author of the Declaration of Independence (1776). Jefferson was one of the most influential Founding Fathers, known for his promotion of the ideals of republicanism in the United States. Jefferson envisioned America as the force behind a great "Empire of Liberty" that would promote republicanism and counter the imperialism of the British Empire.
Major accomplishments during his presidency include the Louisiana Purchase (1803), which doubled the size of the United States, and the Lewis and Clark Expedition (1804–1806), which significantly advanced geographic and scientific knowledge of North America. Jefferson's tenure also saw escalating tensions with both Britain and France, which led to war with Britain in 1812 after he left office. To date, Jefferson is the only president to serve two full terms in office without vetoing a single bill of Congress. Jefferson has been consistently ranked by scholars as one of the greatest of U.S. presidents.
As a political philosopher, Jefferson was a man of the Enlightenment and knew many intellectual leaders in Britain and France. He idealized the independent yeoman farmer as exemplar of republican virtues, distrusted cities and financiers, and favored states' rights and a strictly limited federal government. Jefferson supported the separation of church and state and was the author of the Virginia Statute for Religious Freedom (1779, 1786). He was the eponym of Jeffersonian democracy and the cofounder and leader of the Democratic-Republican Party, which dominated American politics for 25 years. Jefferson served as the wartime Governor of Virginia (1779–1781), first United States Secretary of State (1789–1793), and second Vice President of the United States (1797–1801).
Jefferson, born into a prominent slave owning family, owned hundreds of slaves throughout his life; he held views on the racial inferiority of Africans common for his time and place. Allegations that Jefferson fathered children with his slave Sally Hemings have been made since Jefferson's time.
A polymath, Jefferson achieved distinction as, among other things, a horticulturist, political leader, architect, archaeologist, paleontologist, musician, inventor, and founder of the University of Virginia.