Thomas Jefferson ( April 13 , 1743 -- July 4 , 1826 ) was the third President of the United States , and author of the Declaration of Independence . Thomas Jefferson ( April 13 , 1743 â `` July 4 , 1826 ) was the third President of the United States ( 1801 â `` 1809 ) and the principal author of the Declaration of Independence ( 1776 ) .