This collection is composed of 36 boxes containing approximately 16 linear feet of material. Included in these files are biographical memorabilia, correspondence, manuscripts, journals containing published poetry, and illustrations. The Biographical Memorabilia Series (approx 1.5 feet) includes childhood items such as Boy Scout pins, badges, and uniform pieces; school reports; artwork; and newspaper clippings and wordlists from two national Spelling Bee Contests in which Siegel participated. Later academic material in this series includes certificates, diplomas, assigned papers, and Whale Society Material. Andrew Hudgins' poetry manuscript, Saints and Strangers, sent to Robert Siegel for his comments, also is found in this series.

Siegel's collected correspondence (approx 5 feet) extends over a period of 33 years (1950 1983). Prominent correspondents include editors, publishers, poets, and writers as John Fink, Marsha Lee Masters, John Moffit, Clyde Fixmer, Nuala Archer, and Madeleine L'Engle. The series is arranged chronologically and contains sections of answered and undated correspondence and greeting cards that the family received.

Book manuscripts (3.5 feet) are arranged according to publication date. Included in this series are original manuscripts for The Beast and the Elders, Alpha Centauri, In a Pig's Eye, Whalesong, and The Kingdom of Wundle. There also are duplicate manuscripts, related papers, proofs, and illustrations for some of these works. Manuscripts of the unpublished works "The Man Who Could Fly" and "The Worm of Grog" can also be found here.

The series on poetry manuscripts (approx 3 feet) is alphabetically arranged and contains published as well as unpublished poems arranged to show the revisions they underwent through the years. The series of journals and periodicals (approx 3 feet) contains his published works from 1959 1982 and 1992. Some of the most notable are The Chicago Tribune, The Quest, Beloit Poetry Journal, The Atlantic, and Poetry. Also included in the series is a collection of poems by professors at Dartmouth that was done when Siegel was teaching there in 1970.