Shackelford, James M. was born on July 7, 1827 in Lincoln Company, Kentucky, United States. Son of Edmund and Susan Shackelford.
Academic education at Springfield, Kentucky. Admitted to bar, 1853. Was Lieutenant Company I, 4th Kentucky regiment, in Mexican war: admitted to Kentucky bar, 1853.
Colonel 25th Kentucky infantry, and later of 8th Kentucky cavalry in Union army: became brigadier general, March 17, 1863. Captured Confederate General John H. Morgan and command, July 20, 1863, and later commanded a cavalry army corps, the Army of the Ohio, consisting of 16 regts.