Born in Allegheny, Pennsylvania.Graduate of Western University of Pennsylvania, now University of Pittsburgh. He would become Clapp president of the board of trustees of the University of Pittsburgh and prior to his death he was the oldest living graduate. He was one of the founders and president of Aluminum Company of America. Second cousin of John Henry Clapp.

Clapp had an extensive collection of conch shells that were donated to the Carnegie Museum. His collection of large cents included all the varieties called "collectible" by Sheldon. He exhibited uncirculated large cents at the 1935 ANA convention. His second set of large cents was donated to the Carnegie Institute. An extensive exhibit was prepared when the ANA convention was held in Pittsburgh. In 1937 he donated his first quality set of 1452 large cents to the American Numismatic Society in New York. He died in Pittsburgh.

Author of The United States Cents of the Years 1798-1799 in 1931. One hundred twenty-six cloth bound copies and nine leather bound presentation copies were issued. Author of The United States Cents 1804-1814 as part of the Coin Collector Series in 1941. Author with Howard Newcomb of The United States Cents of the Years 1795-1796, 1797, and 1800 in 1947.

obit: NUM 62 June 1949 page 361; NYT 4/1/49