James Madison is regarded as the principal architect of the U.S. Constitution. As a key figure in the Constitutional Convention of 1787, he played a pivotal role in framing the structure of the new government and articulating the foundational principles of federalism and checks and balances. Madison's contributions also include the drafting of the Federalist Papers, which defended the principles of the Constitution and addressed concerns about its ratification. His vision for a strong yet balanced government has had a lasting impact on the development of American democracy and constitutional law.