Who was the main author of the U.S. Constitution?

James Madison is regarded as the main author of the U.S. Constitution due to his pivotal role in its drafting and his influence in the Federal Convention of 1787. Often referred to as the "Father of the Constitution," he took extensive notes during the convention, capturing debates and decisions that would shape the document. Madison's ideas on the structure of government, separation of powers, and the importance of checks and balances were foundational principles embedded in the Constitution. His contributions were not only limited to the drafting process; he also played a crucial role in promoting the Constitution's ratification through his work in The Federalist Papers, where he, along with Alexander Hamilton and John Jay, articulated the necessity and benefits of the new government structure.