Who called James Madison the father of the Constitution?

James Madison is often referred to as the "Father of the Constitution" due to his pivotal role in drafting and promoting the U.S. Constitution and the Bill of Rights. His contributions during the Constitutional Convention of 1787, including his Virginia Plan, and his advocacy for ratification through the Federalist Papers, significantly shaped the nation's foundational document. This title reflects his influence in establishing the framework of American government and his enduring legacy in American political thought.