Series consists of approximately 2600 pieces of correspondence to and from Dr. J.D. Detwiler. Correspondents include many names prominent in science, conservation and public life, including William A. Albrecht, Ian McT. Cowan, L.A. DeWolfe, J.R. Dymond, Archibald Gowanlock Huntsman , W.W. Judd, Fred Landon, Robert F. Legget, Harrison F. Lewis, Georges Maheux, K.W. Neatby, Ernest C. Oberholtzer, Edward G. Pleva, Dana Porter, D.S. Rawson, A.H. Richardson, R. Omar Rilett, William Rowan, Jacques Rousseau (1905-1970), E.S. Russenholt, T.M. Sonneborn, Robert J.C. Stead, Hugh Templin, Ross B. Willis.

Series consists of 174 pieces of correspondence to and from writers other than John D. Detwiler.