The Wendy Jeffers research material on Niles Spencer measures 3.0 linear feet and dates from circa 1930-2015. The material was compiled by Jeffers for an exhibition and catalog she produced of Spencer's work for the Whitney Museum in 1990 and for research toward an updated catalogue raisonné. The bulk of the collection is comprised of correspondence, provenance research on individual artworks, writing, and photographic material. Jeffers' material expands on Dorothy C. Miller's research completed while organizing a Spencer exhibition at the Museum of Modern Art in 1954.

The records of Jacques Seligmann & Co. measure approximately 203.1 linear feet and date from 1904 to 1978, with bulk dates from 1913 to 1974. The collection includes extensive correspondence files, reference material on American and European collectors and their collections, inventory and stock records, financial records, exhibition files, auction files, and the records of subsidiary companies. The collection is an invaluable resource in tracing the provenance of particular works of art and provides a comprehensive view of the activities of collectors and art dealers in the years leading up to and following World War II.

The Jamison Thomas Gallery records measure 27.2 linear feet and 0.001 Gb and date from 1940-2000, with the bulk of the records dating from 1980-1995, reflecting the years the Gallery operated in Portland Oregon. About 1/2 of the records consist of artists' files of artists represented by the gallery and artists of interest. Also found are administrative records, client and collector files, financial and legal records, exhibition files, and publicity files.

The papers of artist Shirley Jaffe measure 7.1 linear feet and 0.260 GB and date from circa 1950-2011. The collection documents her life and career as an American painter living in Paris through biographical material, letters, notebooks, writings, project files, printed and digital material, photographic material, and sketchbooks.

The papers of art historican August Jaccaci measure 7.2 linear feet and date from 1889 to 1935, with the bulk of the material dating from 1904 to 1914. The collection documents Jaccaci's work as an art historian, writer, and editor, primarily during the period he researched, compiled, and published his book Noteworthy Paintings in Private American Collections. More than one-half of the collection consists of extensive correspondence to and from many notable artists, collectors, and art historians, including John La Farge, Kenyon Cox, Isabella Stewart Gardner, and Bernard Sickert concerning the research and publication of the book. The papers also house legal files, writings and notes, art collection research files, and photographs of artwork.

The papers, 1878-1964 (20.5 linear feet) of museum curator, director, and art scholar William Mills Ivins (1881-1961) consist of correspondence, writings, notes, photographs, and Ivins family papers. Ivins was Curator of Prints, 1916-1946, Assistant Director, 1933-1938, and Acting Director, 1938-1940 at the Metropolitan Museum of Art. The collection contains professional and personal correspondence with art historians, art dealers, museum curators, print and book collectors, and artists concerning the history of print making, book design and illustration, print collectors and collecting, exhibitions, and museum administration. Also found are Ivins' published and unpublished writings and lectures, and notes. The collection contains some Ivins' family papers including family correspondence, genealogies, and photographs.

The papers of Reginald R. Isaacs measure 22.54 linear feet and date from 1842 to 1991, with the bulk of the material from 1928 to 1991. The collection includes Isaacs's personal and professional papers, as well as extensive research material he collected and created for his two-volume biography, Walter Gropius: The Man and His Work.

The Irving Blum Gallery and Ferus Gallery announcements consist of 32 announcements for exhibitions at the Los Angeles Ferus Gallery (1957-1966) and its successor the Irving Blum Gallery (1966-circa 1972). Exhibition announcements are for many exhibitions of southern California contemporary and pop artists, as well as New York artists. Artists represented by announcements include John Altoon, Don Bachardy, Larry Bell, Billy Al Bengston, Robert Irwin, Jasper Johns, Donald Judd, Craig Kauffman, Roy Lichtenstein, Edward Moses, Kenneth Noland, Ad Reinhardt, Ed Ruscha, Frank Stella, and Andy Warhol, among others.

Art dealer Leroy Ireland's research material on George Inness measures 2.0 linear feet and dates from 1916 to 2007, with the bulk of the material dating from 1960 to 1971. The collection documents Ireland's research for his book The Works of George Inness: An Illustrated Catalogue Raisonne through correspondence, research files, and photographs of artwork.

The papers of California conceptual artist and sculptor David Ireland measure 24.8 linear feet and 8.39 GB and date from circa 1910s to circa 2009, with the bulk of the material dating from 1960 to 2005. The papers include biographical material, correspondence, notes and notebooks, installation projects and exhibition files, teaching files, travel files, personal business records, printed and digital material and commercial recordings, photographic materials, artwork, and video and sound recordings.