The "Father of the Constitution" is James Madison. He played a pivotal role in drafting and promoting the United States Constitution and the Bill of Rights. Madison authored the Virginia Plan, which served as the basis for the Constitutional Convention's discussions, and he co-wrote the Federalist Papers with Alexander Hamilton and John Jay to advocate for the Constitution's ratification. Though Madison modestly insisted the Constitution was the work of many, his contributions in shaping the framework of the federal government, establishing checks and balances, and ensuring individual rights earned him this title. He later became the fourth president of the United States, serving from 1809 to 1817.