In 1947, Verner Clapp became Chief Assistant Librarian at the Library of Congress. He served in this position until 1956, when he left the LC to become director of the Council on Library Resources. Clapp played a signficant role in both issues of loyalty oaths and microfilming of materials at the Library of Congress.

Sources:

Louise S. Robbins, "The Library of Congress and federal loyalty programs, 1947-1956" Library Quarterly, Oct94, Vol. 64 Issue 4, p365.

Nicholson Baker, Double Fold: Libraries and the Assualt on Paper (New York: Vintage, 2002), p. 29-34, 83-96