On what date was the U.S. Constitution signed at the convention whose history America250 honors?

The U.S. Constitution was signed on September 17, 1787, at the convention whose history America250 honors.

The signing took place at the Pennsylvania State House in Philadelphia, now known as Independence Hall. Thirty-nine delegates endorsed the document at the close of the Constitutional Convention, which had met for four months to design a stronger federal government.

Signing did not immediately make the Constitution the operating law of the United States. The document required ratification by conventions in at least nine states. Delaware became the first to ratify in December 1787, and the Constitution took effect in 1789 after the required threshold had been reached.

September 17 is now observed as Constitution Day and Citizenship Day in the United States. The date is distinct from July 4, 1776, when Congress adopted the Declaration of Independence.