Architectural plans and renderings of Welch's designs, largely New York City residences, circa 1890s-1920s; specifications; photographs; and brochures advertising buildings at 787 Fifth Ave., 628 Fifth Ave., and 71 and 73 Murray Street, in New York City. Drawings and a sketchbook done by Welch while a student; fourteen notebooks containing Welch's notes from Columbia classes in architecture, 1888-1890; licenses to practice in New York and New Jersey, 1904-1923; a certificate, 1937, and related correspondence relating to Welch's appointment as a U.S. delegate to the fourteenth International Congress of Architects, held in Paris, July 18-25, 1937. A list of U.S. delegates is included. Of note are drawings and papers for the restoration of the Dyckman House, an 18th century farmhouse in upper Manhattan (1910-1917); and the Mrs. Rutherford Stuyvesant Estate in Allamuchy, New Jersey, and the Rutherford Stuyvesant Momument in Tranquility Cemetery, Tranquility, New Jersey, designed by sculptor Daniel Chester French.

This collection contains architectural photographs, drawings and records related to the architectural projects and designs of Warren and Wetmore, principally in the United States, but also representing commissions in Canada, Cuba, and Puerto Rico. Unfortunately, the bulk of architectural drawings produced by the firm are no longer extant. Additionally, it holds a variety of photographs and other records used as reference materials in the course of Warren and Wetmore's professional work. Lastly, a small group of student and personal papers and photographs from Whitney Warren completes the collection.