Correspondence, letterbooks, addresses, lectures, legal memoranda, scrapbooks, printed matter, memorabilia, and other papers relating chiefly to Choate's service as U.S. ambassador to Great Britain, law practice in New York, N.Y., student days at Harvard University, and charitable work in New York; and to Choate family affairs. Documents his service as delegate to the International Peace Conference at the Hague, Netherlands, in 1907; chairman of the New York committee for the 1917 reception of British and French commissions headed by Arthur James Balfour, Earl of Balfour, René Viviani, and Joseph Jacques Césaire Joffre; and service as president of the New York State Constitutional Convention, 1894. Also documents his association with the American Museum of Natural History and the Metropolitan Museum of Art, New York, N.Y.; and his work with Harvard University alumni. Subjects include the American Bar Association; Open Door policy of the U.S. in the Far East; Boxer Rebellion, 1899-1901; treaties of 1900 and 1901 negotiated by U.S. secretary of state John Hay and the British ambassador to the U.S., Baron Julian Pauncefote, pertaining to an interoceanic canal in Central America; the Algeciras Conference of 1906 concerning relations between France and Morocco; the Alaska boundary dispute; and Union League of America.

Family correspondents include his parents, George F. Choate and Margaret Manning Choate; his brother and sister, William Gardner Choate and Caroline Choate; his wife, Caroline Sterling Choate; and their daughter, Mabel Choate. Other correspondents include Charles Francis Adams; Arthur James Balfour, Earl of Balfour; James M. Beck; James Bryce, Viscount Bryce; John R. Carter; Grover Cleveland; George Nathaniel Curzon, Marquess Curzon of Kedleston; Charles William Eliot; William Maxwell Evarts; John Watson Foster; F.V. Greene; John Hay; Henry Charles Keith Petty-FitzMaurice, Marquess of Lansdowne; Edwin T. Morgan; Henry K. Oliver; William Phillips; Robert S. Rantoul; Whitelaw Reid; Theodore Roosevelt; Elihu Root; William V. Rowe; Thomas Henry Sanderson, Baron Sanderson; William H. Taft; Sir George Otta Trevelyan; Henry White; Woodrow Wilson; and Lothrop Withington.