The papers are a small, fragmentary collection documenting the adult life of an army career officer. Because Treat's career spanned frontier duty and the modern warfare of World War I the scarcity of the documentation is particularly disappointing. The collection includes biographical material, clippings, memorabilia, correspondence, diaries, reports, and a subject file on horsemanship.
Biographical material includes a detailed service record, Xeroxed biographical clippings, and memorabilia. The correspondence, which is chiefly incoming, includes both official and personal letters. Among the prominent correspondents are Newton D. Baker, O. O. Howard, Robert Lansing, Thomas Nelson Page, John J. Pershing, William T. Sherman, and Leonard Wood. Although the coverage is quite fragmentary, several items deserve special mention. Among them are a copy of the report which Treat filed in 1917 for the American Expeditionary Force concerning conditions in the British and French armies, a memorandum on the 1924 Olympics, and an estimate of military conditions prepared in 1936 as a retired officer. Personal letters in the collection concern his return from Italy in 1919 and his views on the League of Nations and (in a letter from J. G. Harbord to Treat) conditions in the War Department in 1921.
The diaries include one volume on a trip to Europe in 1892 and two volumes on his travel and assignments in 1918. Several items document Treat's reputation as the “Father of Polo in the American Army” and his love of horses and horsemanship. These include an account book of the Fort Riley Hunt Club (1894-1896), clippings about his participation in polo and jumping competitions, a letter from Theodore Roosevelt (1910) declining to purchase a horse which Treat owned, and records of his champion horse Jacquin. Miscellaneous reports includes a paper on the Monroe Doctrine and a report on artillery service in Cuba during the Spanish American War.
