Allen C. Thomas autograph album and letterbooks

Allen Clapp Thomas was born on December 26, 1846, in Baltimore, Maryland, the son of Richard Henry Thomas, M.D. and Phebe Clapp. He entered Haverford in 1861, and graduated in 1865. While at Haverford, he was the secretary of the Everett Society, a member of the Loganian society, a member of the First Cricket Eleven, and a baseball team player. He was the librarian of the Loganian society in 1865, and the president of the Everett Society. He was the valedictorian of his class and the alumni poet in 1866. After graduating from Haverford, he was involved with the mercantile, shipping, and commission business from 1865 to 1878.

Thomas held a variety of faculty postions at Haverford College, including prefect from 1878 to 1887, professor of history and political science from 1887 to 1893, professor of history from 1893 to 1912, professor of history emeritus from 1912 to 1920, librarian from 1878 to 1915, and consulting librarian and librarian emeritus from 1915 to 1920. He was the editor of the Bulletin of Friends' Historical Society of Pennsylvania and the author or editor of many publications. Some of the organizations of which he was a member include the Baltimore Corn Exchange, American Historical Association, American Society of Church History, American Antiquarian Society, Friends Historical Society of Pennsylvania, Friends Historical Society of London, Maryland Historical Society, Historical Society of Pennsylvania, American Philosophical Society, Pennsylvania Library Club, Phi Beta Kappa, and the American Library Association. He was also the Presiding Clerk of Baltimore Yearly Meeting of Friends (Orthodox) from 1897 to 1920.

Thomas married Rebecca H. Marble in Rhode Island in 1872, and they had two children: Edward Thomas and Miriam Thomas. He died in Haverford, Pennsylvania on December 15, 1920.