Delegates signed the United States Constitution on September 17, 1787, in Philadelphia.
The signing concluded the Constitutional Convention, which had met in the Pennsylvania State House, now known as Independence Hall. Thirty-nine delegates signed the document, while several delegates who opposed it refused to sign or had already left. George Washington, the convention’s presiding officer, signed first, followed by the other delegates.
Signing did not immediately make the Constitution the governing framework for the United States. Article VII sent the document to state ratifying conventions and required approval from nine states. New Hampshire supplied the ninth ratification on June 21, 1788, and the new federal government began operating in 1789.
The signing date is sometimes confused with the date of adoption of the Declaration of Independence, July 4, 1776, or with the Constitution’s effective date. September 17 is now observed in the United States as Constitution Day, making it an especially relevant date during the nation’s 250th-anniversary period.