On what date did delegates sign the United States Constitution, a milestone linked to America250?

Delegates signed the United States Constitution on September 17, 1787.

The signing occurred at the Pennsylvania State House in Philadelphia, the same building where the Declaration of Independence had been adopted. Thirty-nine delegates signed the completed Constitution at the end of the Constitutional Convention. George Washington, who presided over the convention, signed first.

The Constitution did not take effect immediately. It required ratification by nine states, and New Hampshire became the decisive ninth state to ratify it on June 21, 1788. The new federal government began operating in 1789, with Washington inaugurated as president on April 30 of that year.

September 17 is now observed in the United States as Constitution Day and Citizenship Day. The date is separate from July 4, 1776, the anniversary at the center of America250.