James Madison
James Madison is referred to as the Father of the Constitution. He authored the document and provided the structure for the document. He also created the concept for the Bill of Rights and amendment process.
James Madison structured the Constitution on his writing of the Federalist Papers. The Federalist papers provided the reasons why a Constitution was needed and the basic principles of the Constitution. Though other men were involved in the concepts and writing of the Constitution, it is Madison that gets much of the credit for the document. John Adams and Thomas Jefferson both contributed based on their early documents written during the Revolution. Alexander Hamilton also contributed to the Constitution through his contribution of the Federalist Papers.