All 39 delegates to the Constitutional Convention signed the U.S. Constitution in September 1787, but the 40th signature, that of William Jackson, the Secretary of the Convention, authenticated the results of the session in Philadelphia. This booklet on Jackson is one in a series on Revolutionary War soldiers who signed the U.S. Constitution, and it covers his early life, his military service in the southern colonies, and his role as the Constitutional Convention's secretary. Personal data about Jackson and a bibliographic essay of further readings are also included. (DJC)