The The U.S. Constitution established America's national government and fundamental laws, and guaranteed certain basic rights for its citizens. It was signed on September 17, 1787, by delegates to the Constitutional Convention in Philadelphia. The present United States Constitution replaced the Articles of Confederation on March 4, 1789.
The United States Constitution is an amazing document. A bold experiment in democracy more than 200 years ago, it has proved both stable and flexible enough to survive and remain effective in a world totally different from the one in which it was written.