Thirty-nine delegates signed the United States Constitution on September 17, 1787. They endorsed the document at the final session of the Constitutional Convention in Philadelphia.
The convention began as an effort to improve the Articles of Confederation but produced an entirely new framework for federal government. Delegates debated representation, executive power, taxation, and the relationship between state and national authority. Twelve states sent delegates; Rhode Island declined to participate.
The figure 39 is often confused with the 55 delegates who attended at least part of the convention and the 56 signers of the Declaration of Independence. Three delegates who were present—George Mason, Edmund Randolph, and Elbridge Gerry—refused to sign. Several other delegates had already departed.
George Washington presided over the convention and signed the document. Benjamin Franklin, then 81, was the oldest signer. The Constitution became effective after ratification by nine states, as specified in Article VII, and the new federal government began operating in 1789.