Alexander McMillan Welch (1869-1943) was a New York City based architect who practiced independently and as a member of Welch, Smith & Provot. His firm was best known for designing New York City townhouses in the Beaux-Arts style. The collection includes 1,641 architectural drawings, 196 student drawings, 14 student notebooks, 99 loose photographs and 3 photo albums of project photography, project specifications and files, and some professional ephemera.

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 collections includes architectural drawings, files and photographs of projects designed by Woodbridge and his various firms, circa 1928-1960s. These include buildings at Presbyterian Church, Savoonga, St. Lawrence Island, Ala.; Cole Memorial Chapel, Wheaton College, Wheaton, IL; Amherst College, Mass.; Smith College, Mass.; St. Mary the Virgin Church, Chappaqua, N.Y.; St. John's Chapel and Library, Hobart College, Geneva, N.Y.; the Keene Valley Congregational Church, Keene Valley, N.Y.; and the Brick Presbyterian Church and the Episcopal Church Center, both in New York City; as well as other churches, residences, and miscellaneous projects. Also, included are drawings done by Woodbridge while a student at the Columbia School of Architecture, early 1920s; photographs of some of Woodbridge's buildings taken mostly by the architectural photographer Samuel H. Gottscho; a small sample of Woodbridge's correspondence, 1941-1942, documenting his role as chairman of the American Institute of Architects Committee on Architectural Services, relating to the role architects could play in the war effort; sketchbooks of various international locations; and photographs and documents relating to archaeological excavations at Antioch in Pisidia, Turkey.