August Belmont (1813-1890) was a banker, politician, and American agent of the Rothschilds; his son August Belmont (1853-1924) was a financier and sportsman.

Correspondence, copies of letters, documents, manuscripts, invitations, menus, clippings, school papers, leases, agreements, deeds, financial accounts, photographs, and printed miscellany. The papers deal with many aspects of the Belmont family interests from 1799 until 1930, including: finance, banking and the Rothschilds; the United States Navy, Commodore Matthew C. Perry (1794-1858) and the Perry expeditions to Mexico and Japan; Belmont's embassy to The Netherlands from 1853 to 1857; the Democratic Party, New York City politics, presidential and Civil War politics; social life in New York and Newport and European travel; horses, horse breeding, The Jockey Club, polo, the Remount Association (for cavalry horses in World War I), fox hunting, dog breeding, and yachting; New York subway construction, railroads, the Cape Cod Canal and aviation; the Democratic Convention of 1912; and genealogical notes on the Belmont, Perry, and other families. In addition to the correspondence, there are 117 letter books, tissue-paper copies of outgoing letters.