As a result, the Arabian horse collection became one of the world's largest public collections of Arabian horse materials. These papers deal with all aspects of the Ranch from its inception in 1925 until the death of Mr. Kellogg in 1951. From 1925 through 1928 the documents are originals, but the remainder are photocopies from the files of the Kellogg Company. Of particular interest are the series of letters between Mr. Kellogg and Lady Wentworth concerning Lady Wentworth's offer to sell Mr. Kellogg the entire herd at the Crabbet Stud. There are also two letters signed by Rudolph Valentino in which he discusses conditions for the loan of Jadaan for the film, Son of the Sheik.
Periodicals are a significant element in the collection.
All known Arabian horse perodicals are acquired, incuding foreign language publications. Backfiles of current and ceased publications are maintained. An extensive selection of foreign and domestic stud books can be found in the W. K. Kellogg Arabian Horse Library. Countiries in which Arabians are bred on a large scale such as Poland and Spain are represented as are countries breeding Arabians on a small scale such as Belize. Stud books from both government registries and private registries reside in the collection.