There have been 47 vice presidents of the United States, from John Adams to Joe Biden. Originally, the Vice President was the person who received the second most votes for President in the Electoral College. However, in the election of 1800, a tie in the electoral college between Thomas Jefferson and Aaron Burr led to the selection of the President by the House of Representatives. To prevent such an event from happening again, the Twelfth Amendment was added to the Constitution, creating the current system where electors cast a separate ballot for the vice presidency.