Jefferson, Thomas – (Born April 14, 1743; Died natural causes July 4, 1826, Virginia) Third President of the United States of America, (March 4, 1801 – March 4, 1809) chief author of the Declaration of Independence, first Secretary of State, greatly expanded the size of the Country with the Louisiana Purchase, although he had doubts as to whether or not the act of purchase was constitutional. (Democratic Republican)