From 1926 to 1943 Williamson served as Director of the Columbia University Libraries and Dean of the Columbia School of Library Service. Upon retirement he remained active in educational circles as a member of the Greenwich Association for the Public Schools and as consultant to the Connecticut Commission for Educational Television.

Correspondence of Williamson covering his college years and his positions at Bryn Mawr College, the New York Public Library, the Carnegie Foundation, and the Rockefeller Foundation. A significant portion of Williamson's Columbia University correspondence and memoranda is addressed to or related to Roger Howson, University Librarian from 1926 to 1940. The manuscripts, chiefly typescripts, are concerned with library science and educational topics. Also, clippings and pamphlet files with some related correspondence and typescripts dealing with education and particularly the use of television as a teaching aid.