This collection contains letters between Professor Gambrill and Johns Hopkins University affiliates such as Charles Andrews, Sidney Painter, Eric Goldman, and Isaiah Bowman. Further correspondence with H.S. Commager, A.M. Schlesinger, Merle Curti, and Charles and Mary Beard are also included. The collection also contains materials relating to educational policy, Maryland public schools, and the administration of The Johns Hopkins University, as well as papers related to his teaching career at the Columbia Teachers College at Columbia University. The materials in this collection date from 1794 to 1966.