From the desk of Jan Hommel, Museum Director:

Q: Which president instituted the handshake as the official way to greet guests?

A: Thomas Jefferson. For presidents today, shaking hands is just part of the job. Each firm clasp could win a vote or charm a foreign dignitary. But Jefferson, who started the tradition, used it as a way to greet guests simply because it seemed more personal than the formal bow employed by George Washington. President Washington would bow to guests at presidential receptions to avoid physical contact and the tradition lasted through the presidency of John Adams. Washington would rest one hand on a sword and the other holding a hat to avoid the remote possibility of anyone forcing a handshake. Thomas Jefferson ended the tradition of ‘bowing’ by shaking hands when greeting people. Jefferson had no consideration for status: ordinary citizens and high-ranking diplomats received the same unpretentious welcome to the White House. (Smithsonian Presidential Trivia)