Federalists and Anti-Federalists played crucial roles in shaping the U.S. Constitution during the late 18th century. Federalists, including figures like James Madison and Alexander Hamilton, advocated for a strong central government, arguing that it was necessary for maintaining order and unity. They supported the proposed Constitution and wrote the Federalist Papers to promote its ratification. In contrast, Anti-Federalists, such as Patrick Henry and George Mason, feared that a strong central authority would threaten individual liberties and state rights. Their resistance led to the inclusion of the Bill of Rights, addressing concerns about civil liberties and ensuring checks and balances in the new government.