The Constitutional Convention started on May 25th, 1787, four years after the Americans had won their independence. Gathered at the Pennsylvania State House (now known as Independence Hall) were 55 of the most admired and trusted men who have ever walked this soil. Included in that meeting were George Washington, Benjamin Franklin, and James Madison.
For their first four years, the newly founded United States of America muddled along under the Articles of Confederation, which had been drafted shortly before the end of the war. Congress had authority over things like war, currency, and foreign affairs, but no way to garner funds for such endeavors from the individual states. This made the country's governing body almost useless.
The Constitutional Convention lasted for three months hashing out issues like balancing power between the more populated states and the more rural states. It finally ended on September 17, 1787, with 38 of the 41 delegates still present signing the document. But they weren't done. Under their carefully crafted system of checks and balances, the document had to be ratified by at least nine of the thirteen states.
Five states signed almost immediately, but others expressed their concerns that the document didn't address issues like freedom of speech, religion, and the press. Only after reassurances that amendments would be forthcoming did four more states sign on to make the Constitution the legal governing document of the country. It became the law of the land on March 4, 1789, with the first ten amendments - known as the Bill of Rights - to follow on September 25, 1789. Those were ratified by the states on May 29, 1790.
The United States Constitution is the oldest written national constitution in operation today. It was conceived and executed by an incredible assembly of men, quite likely the caliber of which we may never gather together in one place for one cause ever again.
(For the uber-history geeks, there were a total of 19 proposed amendments to the Constitution for Congress to consider. Congress passed 12 of them. The states only ratified 10 into the Bill of Rights. One dealt with how the House of Representatives was seated, the other stated that Congress could not vote itself a pay raise. In 1992, that amendment was finally ratified and became the 27th Amendment to the United States Constitution.)