what were his contributions to the federalist papers?
He co-wrote the The Federalist Papers with  Alexander Hamilton and John Jay to promote the ratification of the United States Constitution.
James Madison
Altogether, Hamilton, Madison, and Jay wrote the 85 essays of what became known as "The Federalist Papers" in the span of six months, with Madison writing 29 of the essays. The articles were also published in book form and became a virtual debater's handbook for the supporters of the Constitution in the ratifying conventions. Historian Clinton Rossiter called "The Federalist Papers" "the most important work in political science that ever has been written, or is likely ever to be written, in the United States." Federalist No. 10, Madison's first contribution to "The Federalist Papers", became highly regarded in the 20th century for its advocacy of representative democracy. In Federalist No. 51, Madison explained how the separation of powers between three branches of the federal government, as well as between state governments and the federal government, established a system of checks and balances that ensured that no one institution would become too powerful.

from what does the 3rd amendment free citizens The Third Amendment as implying a belief that an individual's home should be free from agents of the state. when was it adopted? March 1, 1792 who introduced it? James Madison who was he? An American statesman, diplomat, expansionist, philosopher, and Founding Father who served as the fourth president of the United States from 1809 to 1817. when was he born? March 16, 1751 where was he from? Virginia, United States did he serve in any war? He  served as a member of the Virginia House of Delegates and the Continental Congress during and after the American Revolutionary War. who was he married too? Dolley Payne Todd
wiki:7693325
James Madison [SEP] "The Federalist Papers" and ratification debates
After the Philadelphia Convention ended in September 1787, Madison convinced his fellow Congressmen to remain neutral in the ratification debate and allow each state to vote upon the Constitution. Throughout the United States, opponents of the Constitution, known as Anti-Federalists, began a public campaign against ratification. In response, Alexander Hamilton and John Jay began publishing a series of pro-ratification newspaper articles in New York. After Jay dropped out from the project, Hamilton approached Madison, who was in New York on congressional business, to write some of the essays. Altogether, Hamilton, Madison, and Jay wrote the 85 essays of what became known as "The Federalist Papers" in the span of six months, with Madison writing 29 of the essays.