On what date did delegates sign the United States Constitution, a key America250-era founding milestone?

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

The signing took place at Independence Hall in Philadelphia, where the Constitutional Convention had met for four months. Thirty-nine delegates endorsed the final document that day. The convention’s secretary, William Jackson, also certified handwritten corrections in the text.

The signing date is different from the date the Constitution took effect. The document required ratification by conventions in the states, and the new federal government began operating in 1789. Rhode Island declined to send delegates to the convention and later became the last state to ratify, in 1790.

The Constitution replaced the Articles of Confederation as the framework for the national government. Its signing is not the same event as the Declaration’s adoption in 1776 or the Declaration’s principal signing in August 1776. Together, these milestones form part of the founding history recalled during America250 commemorations.