George Washington (1732-1799) in his first inaugural address urged Congress to propose amendments to the Constitution which provided for "a reverence for the characteristic rights of freemen and a regard for public harmony." He had done this due to the urging of other Founders, including Thomas Jefferson (1732-1826), who had raised the issue of the lack of individual liberties in the Constitution.
Although James Madison (1751-1836) dutifully introduced proposed amendments to the First Congress on June 8, 1789, Washington, among other Founders and Congressmen, had had a hand in drafting and supporting the original bill. Seventeen proposed amendments were passed by the House of Representatives on August 24, 1789. These were then reduced to twelve amendments passed by both the House and Senate, which then went to the states to be ratified. Ten of these were finally ratified on December 15, 1791. Surprisingly, one of the two amendments initially not ratified by the states had to do with compensation for the members of Congress, but it was finally ratified as the 27th Amendment on May 7, 1992, over 200 years later!
The Bill of Rights was not written by any one person. Instead, it was created by Congress as a whole.
During the ratification of the Constitution, the Federalists promised to add a bill of rights to the Constitution. They made this promise because many people in the country were worried about the federal government having too much power under that Constitution.
The process of writing the Bill of Rights started with James Madison, who was also seen as the main architect of the Constitution itself. George Mason and Thomas Jefferson were also involved. Madison created a set of amendments that he proposed to the House of Representatives. What he proposed was a set of clauses that he wanted inserted into the Constitution. In other words, he did not label his proposals as the First Amendment, the Second Amendment, and so forth.
The House did not accept the idea of inserting new words into the Constitution. Instead, it decided to propose 17 amendments to be added to the end of the Constitution. These were then sent to the Senate. The Senate narrowed them down to 12 amendments. Of those 12 amendments, the states ratified 10. Those 10 came to be known as the Bill of Rights.
Thus, if we are going to give credit for the Bill of Rights to one person, it would have to be Madison. But it is not as if he and he alone wrote the words that are now in the Bill of Rights.
James Madison wrote the Bill of Rights however Washington and members of Congress drafted the original 17 down to 12 and then 10.
President Washington and almost half of the ninety-one members.