The James Gates Percival Papers consist of writings, notebooks, personal papers, correspondence, maps, and other papers. Writings are autograph manuscripts of poetry and prose compositions on linguistics, geology, and geography, including several drafts of his Report on the Geology of Connecticut, as well as chemistry notes by West Point professor James Cutbush. Percival's notebooks contain writings and notes on a broad range of topics in addition to classroom notes from school, college, and his medical school days. Personal papers include contracts, agreements, and subscriber lists related to his publications, inventories and invoices documenting his large library collection, and other financial papers, primarily bills for personal expenses including room, board, and clothing. Correspondence files hold letters to and from many prominent colleagues and scholars such as Benjamin Silliman and Edward C. Herrick in New Haven, friends including George Hayward in Boston, his publishers Sidney Babcock, Samuel G. Goodrich, and Samuel Walker, and editors such as Eliza Leslie and Louisa C. Tuthill. Percival was a member of the New Haven Sing-Song Club and the collection documents his contributions to that organization. Also present is a portrait painting of Percival by his brother Edwin Percival, and small groups of papers regarding Percival's life and work complied by J. H. Ward, Herbert E. Gregory, and others, including a memoir of him by Caroline Howard Gilman.