The papers of William Gay Ballantine, consisting primarily of Ballantine family papers (1750-1913), provide no documentation of Ballantine's tenure as President of Oberlin College (1891-96). Ballantine's personal papers are few but include correspondence(1865-86), three journals (1881-96, n.d.), miscellaneous papers(1836-1933), and writings (1836-1933). The collection also contains several albumen portraits of the Ballantine family (ca. 1846-99). Materials are divided into two record series: Series 1, Ballantine Family Papers and Series 2, William Gay Ballantine Papers. Within Series 1, files are chronologically arranged; within Series 2, files are alphabetically arranged by type of material.

Ballantine antecedents for whom documentation exists include the Rev. John Ballantine (1716-1776), William Gay's great-grandfather; Dr. Ebenezer Ballantine (1756-1823), the grandfather; and the Rev. Elisha Ballantine (1809-1886), Ballantine's father.Elisha Ballantine's correspondence includes letters written from Halle, Germany to friends in Virginia (1834-35) and letters (1862-85) to family written while he was Professor of Greek and Acting President (1879-80) at the University of Indiana, Bloomington.

Ballantine's correspondence (1865-86), predating his presidency of Oberlin, includes three letters (1873) written while serving with the American Palestine Expedition and several letters (1880-86) to his father from Oberlin describing his teaching, his family life, and his theological views. Ballantine's journals include two travel diaries (1881-1902, 1887-96) and a journal containing both reading notes and genealogical notes (n.d.). Among Ballantine's miscellaneous papers are letters of reference for the Palestine Expedition (1873); notice of his receipt of the honorary D.D. degree from Marietta College (1885); various scholastic certificates and his marriage certificate; and a book contract with Houghton Mifflin for The Riverside New Testament (1930). Ballantine's writings are represented by several published sermons in pamphlet form as well as manuscript drafts and newspaper articles.