Who were the Federalists and Anti-Federalists?
In the debate over ratification of the Constitution, two groups emerged. Those who supported the new Constitution were known as Federalists. Those who opposed the new Constitution were known as Anti-federalists. There were several arguments made by the Anti-federalists against ratification of the Constitution. First, they argued that the Constitution gave too much power to the national government at the expense of the states. They also argued that there was no bill of rights. The Federalist countered with several arguments of their own. They said that there were built in safeguards against the federal government becoming too powerful and dominating the states. First, there was the idea of separation of powers where the government would be divided into three separate branches, each with its own powers. Next there was a system of checks and balances whereby each branch of government was given the ability to check the power of the other two branches of government. And finally, there was the idea of federalism, where power would be divided between the federal government (that is, the national government) and the state governments. Some powers would be given or delegated only to the federal government, some powers would be reserved to the states, and some powers would be shared—both the federal government and state governments would have that power. Perhaps the best known Federalists were John Jay, Alexander Hamilton and James Madison who anonymously wrote a series of essays that appeared on a regular basis in four out of five newspapers in New York City. No one knew who the real authors were at the time. The essays, called The Federalist Papers, explained the reasoning behind the new Constitution and argued for its ratification. There were 85 essays in all. In the end, the Federalist prevailed, with all states eventually ratifying the Constitution. The Anti-federalists also won a victory when it was agreed upon to add a bill of rights to the new Constitution shortly after being ratified.
You are referring to the two main groups, and later political parties, that were associated with the Constitutional Convention and the early administration of the United States government. Federalists were the reformers who called for the convention, because they felt the Articles of Confederation had become unworkable, that they were fatally flawed and we should go back to the drawing board. They wanted a stronger central government with the authority to tax, raise an army, and otherwise conduct the affairs of state necessary to any effective government. Prominent Federalists included Alexander Hamilton, George Washington, John Adams and Ben Franklin, among others.
Anti-federalists were nervous about this. They felt it was a power grab and that the revolution they had fought so hard for would devolve into a monarchy if they allowed the Federalists to gain more power. They wanted more power to the states and they wanted guarantees of individual rights. Leaders in the Anti-federalist camp included Thomas Jefferson and James Madison.