Thomas Jefferson Jefferson, Thomas (1743-1826), third president of the United States (1801-1809) and author of the Declaration of Independence. He was a philosopher, educator, naturalist, politician, scientist, architect, inventor, pioneer in scientific farming, musician, and writer. Jefferson was the foremost spokesperson of his day for democracy. As president, he strengthened the powers of the executive branch of government. He was also the first president to lead a political party. Jefferson had great faith in popular rule and sought to develop a government that would best assure the freedom and well-being of the individual. Jefferson was born in western G