The American (U.S.) Constitution was written during the Constitutional Convention in Philadelphia in the summer of 1787 and was completed and signed on September 17, 1787.

Quick Scoop

  • Main writing period: Late May to mid‑September 1787, during the Philadelphia (Constitutional) Convention.
  • Location: Assembly Room of the Pennsylvania State House in Philadelphia, now called Independence Hall.
  • Key date: The finished Constitution was signed by delegates on September 17, 1787, which is often treated as the landmark date for when it was “written.”
  • Historical context: Delegates originally met to revise the weaker Articles of Confederation but ended up drafting an entirely new framework of government.

In everyday usage, when people ask “when was the American Constitution written,” the most precise short answer is: in 1787, and formally completed and signed on September 17, 1787, in Philadelphia.

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