On October 27, 1787, the first of the Federalist Papers appeared in a New York newspaper. Written under the pen name “Publius” by Alexander Hamilton, James Madison, and John Jay, the essays defended the proposed U.S. Constitution. They answered criticisms that the new government would be too powerful or threaten liberty. The authors explained concepts such as separation of powers and checks and balances. The essays influenced ratification debates in several states. Today, they remain important sources for understanding the framers’ intentions and constitutional interpretation.