Collection includes personal and professional correspondence (chiefly incoming), contracts, sketches, diaries, scrapbooks, manuscripts of published and unpublished writings, and "written" conversations between Tilden, who was deaf, and others. Also includes medals, other personal memora bilia. Principal correspondents are his daughter, Gladys Tilden, James D. Phelan & Alexander Stirling Calder.

Series 5: Sculpture,  1889-1970, is arranged alphabetically by name of sculpture or sketch. These files contain a miscellany of contracts, agreements, specifications, newspaper clippings, insurance papers, and notes, etc. Sketches are preliminary drafts of particular sculptures like The Bridge or of ideas such as serpents or architectural ornamentation. An oversize folder also contains sketches. Two folders about inventions can be found here.