Thomas Jefferson (1743-1826) was a 'Founding Father' and third President of the United States. He is known as the principal author of the Declaration of Independence. Jefferson was an advocate of religious freedom, individual and states' rights, and opposed the expansion of federal powers including the Alien and Sedition Act. He is believed to have been an atheist. As President, Jefferson organised the Louisiana purchase from France, and signed the government's Act Prohibiting Importation of Slaves in 1807, though was himself a slave owner.