Madison's constitutional role came first. The son of a Virginia planter, he spent the Revolutionary War and its aftermath in state and national government, where he experienced failure and dysfunction firsthand. In 1786, he maneuvered a conference on interstate commerce in Annapolis, Md., into a call for a Constitutional Convention. When the convention assembled in Philadelphia in 1787, Madison attended every session, from May to September, speaking more than almost anyone else, and keeping notes of every motion and speech.
After the Constitution went to the states for approval, Madison led the fight for ratification in Virginia, then the nation's largest state. He was also a key player in New York, where he wrote a series of pro-Constitution op-eds for local newspapers along with Alexander Hamilton and John Jay; today they're known as the Federalist Papers. And in 1789, Madison, then a congressman, shepherded the Bill of Rights through the House.
Madison was more than just busy; he was intellectually creative. Throughout history, most republics had been city-states, and theorists argued that citizen oversight could work only in small communities. If that was true, it was bad news for the United States, which already stretched from Maine to Georgia in Madison's day. But in Federalist No. 10, Madison made a new argument: that republican government would be more stable in a big country, because selfish factions would find it harder to seize power over an "extend[ed] sphere."
