Which is George Mason's greatest contribution to the United States? A.
writing most of the U.S. Constitution

B.
leading the support for the Bill of Rights

C.
convincing states to ratify the U.S. Constitution

D.
proposing the compromise that led to the U.S. Constitution

Answer:  B. Leading the support for the Bill of Rights.

Explanation:

George Mason was part of a committee working on a constitution for the state of Virginia in 1776, and authored a Declaration of Rights to be included in that Constitution.  The Virginia Declaration of Rights, authored by Mason, became the basis for the Bill of Rights that later became part of the United States Constitution.

In September, 1787, Mason was part of the Constitutional Convention for the United States held in Philadelphia.  As reported by the Smithsonian Magazine (April 30, 2000), "Toward the end of the Constitutional Convention in Philadelphia, Mason proposed that a bill of rights preface the Constitution, but his proposal was defeated. When he refused to sign the new Constitution, his decision baffled some and alienated others, including his old friend, George Washington. Mason's stand nonetheless had its effect. At the first session of the first Congress, Madison introduced a Bill of Rights that paralleled Mason's Declaration of Rights of 1776."