Founding Father and author of the Declaration of Independence. Third president of the United States. Embraced the principles of Republicanism. Served in the Continental Congress, representing Virginia. Was George Washington's Secretary of State. In opposition to Alexander Hamilton's Federalism, Jefferson and his close friend, James Madison, organized the Democratic-Republican Party, and later resigned from Washington's cabinet. Elected Vice President in 1796 in the administration of John Adams, Jefferson opposed Adams, and with Madison secretly wrote the Kentucky and Virginia Resolutions, which attempted to nullify the Alien and Sedition Acts. Composed the Northwest Ordinances. Oversaw acquisition of the vast Louisiana Territory from France (1803), and sent out the Lewis and Clark Expedition (1804-1806), and later three others, to explore the new west. Jefferson doubled the size of the United States during his presidency. Jefferson was a leader in the Enlightenment.