On what date was the U.S. Constitution signed, a milestone included in America250's founding-era story?

The United States Constitution was signed on September 17, 1787, at Independence Hall in Philadelphia.

The signing concluded the Constitutional Convention, which had met for four months to revise the Articles of Confederation. Instead of merely amending the existing system, the delegates produced a new framework for a federal government with separate legislative, executive, and judicial branches.

Thirty-nine delegates endorsed the final document. They represented twelve states because Rhode Island declined to send delegates to the convention. George Washington, who chaired the convention, signed along with figures including Benjamin Franklin, James Madison, and Alexander Hamilton.

Signing did not immediately put the Constitution into operation. It required ratification by the states, and the new federal government began functioning in 1789. September 17 is now Constitution Day in the United States. The date should not be confused with June 21, 1788, when New Hampshire became the ninth state to ratify, or March 4, 1789, when the constitutional government was scheduled to begin.