The anti-Federalists and their opposition to ratifying the Constitution were a powerful force in the origin of the Bill of Rights to protect Amercians' civil liberties. The anti-Federalists were chiefly concerned with too much power invested in the national government at the expense of states. (Howard Chandler Christy's interpretation of the signing of the Constitution, painted in 1940.)
The Anti-Federalists opposed the ratification of the 1787 U.S. Constitution because they feared that the new national government would be too powerful and thus threaten individual liberties, given the absence of a bill of rights.
Their opposition was an important factor leading to the adoption of the First Amendment and the other nine amendments that constitute the Bill of Rights.
The Constitution, drafted at the Constitutional Convention of 1787, needed to be ratified by nine or more state conventions (and by all states that wanted to take part in the new government). A clash erupted over ratification, with the Anti-Federalists opposing the creation of a strong national government and rejecting ratification and the Federalists advocating a strong union and adoption of the Constitution.