French, William M. Life, Speeches, State Papers and Public Services of Gov. Oliver P. Morton. Cincinnati: Moore, Wilstach, & Baldwin, 1864.
Nugent, Helen Jean M. Louis Riel and Oliver P. Morton: The Oddest Couple. Indiana Magazine of History 79 (March 1983): 61-79.
U.S. Congress. Memorial Addresses on the Life and Character of Oliver P. Morton (a Senator from Indiana). 45th Cong., 2d sess., 1877-1878. Washington: Government Printing Office, 1878.
Walker, Charles Manning. Sketch of the Life, Character, and Public Services of Oliver P. Morton. Indianapolis: Indianapolis Journal, 1878.