On what date was the United States Constitution signed, a milestone highlighted by America250?

The United States Constitution was signed on September 17, 1787, a milestone highlighted by America250.

The signing took place at the Pennsylvania State House in Philadelphia, after months of debate at the Constitutional Convention. Thirty-nine of the 42 delegates still present signed the document. Three delegates—George Mason, Edmund Randolph, and Elbridge Gerry—refused to sign because they objected to parts of the proposed system.

The signing did not immediately put the Constitution into operation. It required ratification by conventions in at least nine states. Delaware became the first state to ratify, on December 7, 1787, while Rhode Island was the last of the original 13 states, ratifying on May 29, 1790.

September 17 is observed in the United States as Constitution Day and Citizenship Day. The date is sometimes confused with the Constitution’s effective date, March 4, 1789, when the new federal government began operating under it.