George Mason IV was an American Patriot, statesman and a delegate from Virginia to the U.S. Constitutional Convention. Along with James Madison, he is called the "Father of the United States Bill of Rights." For these reasons he is considered one of the "Founding Fathers" of the United States.
Like anti-federalist Patrick Henry, Mason was a leader of those who pressed for the addition of explicit States rights and individual rights to the U.S. Constitution as a balance to the increased federal powers, and did not sign the document in part because it lacked such a statement. His efforts eventually succeeded in convincing the Federalists to add the first ten amendments of the Constitution. These amendments, collectively known as the Bill of Rights, were based on the earlier Virginia Declaration of Rights, which Mason had drafted in 1776.
On the nagging issue of slavery, Mason walked a fine line. Although a slaveholder himself, he found slavery distasteful for a variety of reasons. He wanted to ban further importation of slaves from Africa and prevent slavery from spreading to more states. However, he did not want the new federal government to attempt to ban slavery where it already existed, because he anticipated that such an act would be difficult and controversial.