The Anti-Federalists were opponents of the ratification of the U.S. Constitution in 1788. The Anti-Federalists were local leaders and never formed alliances across state lines; they never formed an actual party. By contrast the Federalists of 1787-88, led by George Washington, Alexander Hamilton and James Madison, were nationally oriented and cooperated across state lines. This cooperation enabled the Federalists to secure ratification in all 13 states. They were defeated in each state by the Federalists and the Constitution was ratified by all 13 states, going into effect in 1789 with George Washington as the first president.
The Anti-Federalists were local leaders and never formed alliances across state lines; they never formed an actual party. By contrast the Federalists were nationally oriented and cooperated across state lines. This cooperation enabled the federalists to secure ratification in all 13 states. Prominent Anti-Federalists included Patrick Henry and George Mason in Virginia and George Clinton in New York. Thomas Jefferson, then the minister to France, was dubious about the new document but did not publicly oppose it.
The Anti-Federalists argued that the Constitution would create a new federal government that was more powerful than the state governments. They instead wanted powerful state governments. In response to those who supported the Constitution by claiming that it limited federal power, the Anti-Federalists cited two gaping holes in the limitation on federal power: the Necessary and Proper Clause and the Supreme Court. Congress could interfere with the rights of states and the people using the former, and the Supreme Court could construe federal power very broadly. History proved the Anti-Federalists right in some respects.
Concerned that the Constitution contained no guarantee of individual liberties, the Anti-Federalists pressed for the document to be amended. Their insistence led to the creation of the Bill of Rights by James Madison in 1791. 
Just as supporters of ratification of the U.S. Constitution wrote under pseudonyms, Anti-Federalists did also. Names used included Brutus and Federal Farmer. After ratification in 1788 the Anti-Federalists kept quiet and they all supported the new government. By 1795 most were supporting the Democratic-Republican Party (or "Republicans") that Jefferson organized in the mid-1790s. However, some, including Patrick Henry, joined the Federalist Party, which Alexander Hamilton formed in the early 1790s. Madison, a leader of the Federalists in 1787-88, became a leader of the Republicans.
- Ferling, John. A Leap in the Dark: The Struggle to Create the American Republic (2003) online edition
- Levy, Leonard, and Dennis J. Mahoney, eds. The Framing and Ratification of the Constitution (1987), articles by scholars
- Main, Jackson Turner. The Antifederalists: Critics of the Constitution (1961)
- McDonald, Forrest. The Formation of the American Republic, 1776-1790 (1965), by a leading Conservative historian
- McLaughlin, Andrew C. The Confederation and the Constitution, 1783-1789 (1905) 348 pp. online from Google
- Morris, Richard B. The Forging of the Union: 1781-1789 (1987), standard survey of era by leading scholar
- Rutland, Robert Allen. The Ordeal of the Constitution: The Anti-Federalists and the Ratification Struggle, 1787–1788 (1966)
- Note that the "Federalists" of 1787-88 refers to supporters of the new Constitution; and the "Federalists" of the 1790s refers to members of a new party that was created after 1792. Many of the same people were involved, but the two meanings of "Federalist" are often confused.