About noon on the steps of the U.S. Capitol Building, the President-elect takes the Oath of Office, repeating the words enshrined in the Constitution and spoken on that day by the Chief Justice of the United States:
I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States.
Most Presidents have added the words "so help me God" at the end of the oath of office.
Then, it is the President's turn to speak. This is the Inaugural Address. Every elected President since George Washington has given an inaugural address.
Washington, in his second inaugural address, gave the shortest ever by a President, just 135 words. The longest inaugural address, at 8445 words, was delivered by William Henry Harrison, who spoke without a hat or coat in freezing weather and caught a cold that killed him one month later.
The Vice-president-elect also takes his or her oath of office, in the same ceremony, before the President does.
A great many people attend the inauguration of a President, including the outgoing President. The U.S. Military is on hand as well, since the President is Commander-in-Chief of the Armed Forces.
After the inauguration, both President and Vice-president travel in a parade down Pennsylvania Avenue in Washington, D.C., from the Capitol Building to the White House.