After the U.S. Constitution was drafted in 1787, it had to be ratified by at least nine of the thirteen states to go into effect.

This led to a nationwide debate between the Federalists, who supported the new Constitution, and the Anti-Federalists, who opposed it.

The Anti-Federalists feared that the Constitution created a central government that was too powerful and would threaten individual liberties.

The Federalist Papers were a series of 85 essays written to persuade the public, particularly in the key state of New York, to ratify the Constitution.

The essays were written under the collective pseudonym 'Publius' by Alexander Hamilton, James Madison, and John Jay.

They provided a detailed explanation and defense of the principles of the Constitution, such as the separation of powers and checks and balances.

Federalist No. 10, written by Madison, famously argued that a large republic would be better able to control the dangers of factionalism.

Federalist No. 51, also by Madison, explained how the separation of powers would protect liberty.

The promise by the Federalists to add a Bill of Rights after ratification was crucial in winning over several states.

The Federalist Papers are considered one of the most important works of American political philosophy and a key commentary on the Constitution.