The United States Constitution received its final signature at the Philadelphia Convention on September 17, 1787. Thirty-nine delegates signed the document before the convention adjourned.
The convention met from May to September 1787 at the Pennsylvania State House in Philadelphia, the same building associated with the Declaration of Independence. Delegates originally gathered to revise the Articles of Confederation but instead designed an entirely new federal framework.
The Constitution did not take effect on the signing date. It required ratification by the states, and New Hampshire became the ninth state to ratify it on June 21, 1788. The new federal government began operating in 1789.
The signing date is therefore distinct from ratification and inauguration dates. Its connection to America250 lies in the broader founding era that followed the 1776 independence declaration and shaped the nation's government.