The papers of New York museum director and independent curator Thomas M. Messer measure 4.6 linear feet and date from 1949-2010. Material includes correspondence, a diary transcript, and printed material that reflect Messer's long career, primarily as director of the Solomon R. Guggenheim Foundation. Correspondence comprises the bulk of the collection and documents the relationships he built with artists, art historians, curators, and others colleagues. Notable correspondents include Francis Bacon, Will Barnet, Larry Bell, Alberto Burri, Pol Bury, Marc Chagall, Chryssa, Jean Dubuffet, Max Ernst, Dan Flavin, Helen Frankenthaler, Alberto Giacometti, Richard Hamilton, Jean Hélion, Grace Knowlton, Rosemarie Koczy, Jirí Kolár, Katharine Kuh, Agnes Martin, Henry Moore, George Rickey, Charles Simonds, Clyfford Still, Jack Tworkov, and many others.

The Barbara Rose papers date from 1962 to circa 1969 and measure 1.4 linear feet. Papers include letters, writings, printed material, interviews with artists, panel discussions, and lectures relating to Barbara Rose's research as an art historian.

The Samuel J. Wagstaff papers, circa 1932-1985 comprise 6.4 linear feet of correspondence, writings, miscellaneous records, printed material, and photographs documenting Wagstaff's professional and personal relationships with artists and photographers, his career as an art curator, and his position as an important collector of paintings and photographs. Correspondence with artists and others such as curators, arts organizations, galleries, and museums, reflects the diversity of contemporary American art and includes individuals associated with the abstract expressionist, Fluxus, pop, earth, conceptual, and minimalist art movements.

The papers of photographer, filmmaker, and painter Rudy Burckhardt measure 5.6 linear feet and date from 1934 to 2015. A bulk of the collection consists of black and white negatives which document over 260 mid-to-late twentieth century modern artists, their work, studios, and/or exhibitions. Notable artists include Willem de Kooning, Dan Flavin, Joseph Cornell, Helen Frankenthaler, Donald Judd, Franz Kline, Roy Lichtenstein, Louise Nevelson, Isamu Noguchi, Frank Stella, and many others. Burckhardt was hired to photograph for a number of New York art galleries such as the Leo Castelli Gallery and Green Gallery; art collectors including Chaim Gross and David Rockefeller; and art magazines such as ARTnews. Personal papers include announcements and an exhibition catalog; clippings; photographs on postcards; and a book, entitled Conversations with Rudy Burckhardt About Everything, by Simon Pettet, 1987. A small but rich addition to the collection dates from 1941-2015 and contains a curriculum vitae; letters from Joe Brainard, Harold Schimmel, and others; writings; one scrapbook dating from World War II containing letters Burckhardt wrote to Edwin Denby; printed announcements and clippings; and one photograph of Burckhardt taken by Yvonne Jacquette.

The Dwan Gallery records measure 2.3 linear feet and consist primarily of files of exhibitions curated by Virginia Dwan at Dwan Galleries in Los Angeles (1959-1967) and New York (1965-1971). Found within this nearly comprehensive set of exhibition files may be lists of exhibited works, price lists, photographs, slides or color transparencies of installations, invitations, full-size posters, magazine and newspaper clippings and exhibition catalogs.

The papers of southern California Pop artist Billy Al Bengston measure 10.4 linear feet and date from circa 1940s to 1989, with the bulk of the materials dating from 1960 to 1988. The collection documents the life and work of the artist through biographical materials, correspondence, personal business records, gallery and museum files, teaching files, project and commission files, scattered artwork, printed materials, and photographs.

The papers of Los Angeles art critic and writer, art historian, professor, collector, and artist Fidel Danieli (1938-1988) measure 8.4 linear feet and date from 1962 to 1987. Found within the papers are writing and research files, and 108 sound recordings of interviews with or about 45 Los Angeles artists conducted by Danieli in 1974-1975 for the U.C.L.A. oral history project "L.A. Community Artists." There are also sound recordings of art performances and art talks, and printed materials, including numerous exhibition announcements.

The papers of sculptor, writer, and earthworks artist Robert Smithson and his wife, sculptor, filmmaker, and earthworks artist Nancy Holt measure 15.1 linear feet and date from 1905 to 1987, with the bulk of the material dating from 1952 to 1987. The papers consist of Smithson's biographical material; business and personal correspondence, much of it with artists; interview transcripts; extensive writings and project files; financial records; printed material; a scrapbook of clippings; holiday cards with original prints and sketches; photographic material; and artifacts. Also found are project files related to Nancy Holt's motion picture film Pine Barrens and her seminal environmental work of art Sun Tunnels, including a video documentary about Sun Tunnels.

The Leo Castelli Gallery records measure 215.9 linear feet and 0.001 GB and date from circa 1880-2000, with the bulk of the materials dating from the gallery's founding in 1957 through Leo Castelli's death in 1999. The major influence of dealer Leo Castelli and his gallery on the development of mid-to-late twentieth century modern art in America is well-documented through business and scattered personal correspondence, administrative files, exhibition files, extensive artists' files and printed materials, posters, awards and recognitions, photographs, and sound and video recordings. Also included are records for the subsidiary firms of Castelli Graphics and Castelli/Sonnabend Tapes and Films.

The records of Castelli Graphics measure 45.7 linear feet and date from 1965 to 2001. Administrative files, correspondence, exhibition and project files, artists' files, financial and legal records, inventory and stock records, printed materials, and photographic materials document the activities of the New York art gallery and publishing firm founded by Antoinette Castelli.