America Under Thomas Jefferson - Louisiana Purchase By Lunariette Mar 4, 1800 Thomas Jefferson becomes President Apr 20, 1800 US federal offices are moved to DC Apr 20, 1801 Robert Fulton invents Human-Powered Submarine Apr 20, 1801 US War with Barbary States is declared Apr 20, 1801 Thomas Pinckney begins to negotiate with Spain for Florida Apr 20, 1802 US military academy is established in West Point, NY Mar 1, 1803 Ohio becomes a state Apr 20, 1803 Supreme Court can now rule laws unconstitutional Apr 20, 1803 Chemist John Dalton develops theory of the atom Apr 20, 1803 Fort Dearborn (Chicago) is established Jul 4, 1803 Louisiana Purchase Apr 15, 1804 Alexander Hamilton is killed in a duel with Aaron Burr Apr 20, 1804 Napolean becomes emperor of France May 14, 1804 Lewis and Clark Expedition Begins Apr 20, 1805 War with Barbary States ends Apr 20, 1806 Zebulon Pike explores the Southwest Apr 20, 1806 Noah Webster publishes an American dictionary Sep 23, 1806 Lewis and Clark expedition ends Apr 20, 1807 Robert Fulton creates the first successful steamboat service Apr 20, 1807 Embargo Act and Non-Importation Acts are put into action Apr 20, 1807 Aaron Burr sneaks out of America to avoid murder charges Apr 20, 1808 James Madison becomes president Apr 20, 1808 Congress makes importing slaves into America illegal