Final answer:
The U.S. Constitution was written in Philadelphia, Pennsylvania by a group of men during the Constitutional Convention of 1787. It replaced the Articles of Confederation, which had been in effect since 1781.
Step-by-step explanation:
The U.S. Constitution was written in Philadelphia, Pennsylvania by a group of men during the Constitutional Convention of 1787. This group of delegates met to revise the Articles of Confederation but instead created a new framework for a national government, leading to the creation of the U.S. Constitution. The Constitution replaced the Articles of Confederation, which had been in effect since 1781.