Rittenhouse Square, one of the William Penn's original five, was known as the southwest square until 1825 when it was named for the astronomer-clockmaker, David Rittenhouse (1732-96). This amazing man of universal talents - one of many in 18th century Philadelphia - was a descendant of William Rittenhouse, who built the first paper mill in America in Germantown. He was at various times a member of the General Assembly and the State Constitution Convention, and president of the Council of Safety. His survey of the Maryland-Pennsylvania boundary in 1763-64, to settle a dispute between the Penns and Lord Baltimore, was so accurate it was accepted and followed by Charles Mason and Jeremiah Dixon when they surveyed the "line" for which they are still remembered. Professor of Astronomy at the University of Pennsylvania and inventor of the collimating telescope, he was also president of the American Philosophical Society and the first director of the United States Mint.