"Following the forced resignation of Under Secretary of State Sumner Welles in 1943, Messersmith, then Ambassador to Mexico, was rumored to be on a short list of candidates to succeed him, but Roosevelt instead selected future Secretary of State Edward Stettinius, Jr..

Messersmith's collection of papers has been digitized and made available to researchers by the University of Delaware.The digitization project was made possible through a grant from the National Historical Publications and Records Commission (NHPRC).