The collection consists primarily of materials gathered by Princeton University librarian Julian Boyd for a proposed book of H. L. Mencken's letters. Transcripts, made for Boyd by Mencken's secretary from her original shorthand notebooks, and microfilm copies of letters from Mencken to others, including Theodore Dreiser and Upton Sinclair, comprise the bulk of the collection. The collection also includes Boyd's correspondence with other people possessing letters from Mencken, as well as Boyd's initial selection of letters for his book. Much relates also to Ernest Boyd's published work Mencken (1925). In addition, the collection contains a number of original letters from Mencken to others, including an undated letter to F. Scott Fitzgerald; the corrected galley proofs of A New Dictionary of Quotations (1942); typescripts of a poem, "Elegy in C Minor," and a speech given at the annual dinner of the American Philosophical Society; guides to book reviews in The American Mercury (Vols. 1-30, 1924-1933) and The Smart Set (Vols. 28-72, 1908-1923); and photographs.