George Washington oversaw its construction, but the first President to move in was John Adams, in 1800, and it has been the private residence of every President since (although it was not until Theodore Roosevelt moved in that it was formally named The White House). The original residence in the center includes the state floor and second floor family residence; the West Wing extension houses the Oval Office and Cabinet Room, the East Wing, added in 1942, provided additional office space.
If you go:
Tours are available on a first-come first-served basis; requests must be made through your Member of Congress no less than 21 days in advance, and you will need a valid US identity card or passport.
Links:

1600 Pennsylvania Ave NW
Washington, DC 20500-0004 USA
info@whitehouse.gov
Phone Numbers:
Switchboard
+1 (202) 456-1414
+1 (202) 456-1414
Message from RoadTrip America