March 4th is among the most significant days of the year in the history of the United States Government.
The Constitution was approved on September 17, 1787. The required ninth state, New Hampshire, ratified the Constitution on June 21, 1788. On September 13, 1788, the Confederation Congress approved an act that called for “the first Wednesday in March next to be the time for commencing proceedings under the Constitution.”
The first Wednesday the following March was the 4th day of March, and hence the terms of the President and Vice President and members of Congress began on March 4, 1789. As it turned out, the first Congress convened on March 4, but did not actually have a quorum in either house until early April. Washington did not take the oath of office until April 30, 1789.
But officially it all began on March 4, 1789.
Thirty-six times — every fourth year for 144 years — March 4th was inauguration day. The 20th Amendment changed it to January 20, and Congress to January 3, effective October 15, 1933.