Benton, James Gilchrist was born on September 15, 1820 in Lebanon, New Hampshire, United States. Son of Calvin and Mary (Gilchrist) Benton.
Graduated from the United States Military Academy, 1842.
Brevetted Second lieutenant United States Ordnance Corps, 1842, second in command Lieutenant, 1847, First lieutenant, 1848, captain, 1856. Instructor ordnance and gunnery United States Military Academy, 1857-1861. Principal assistant to chief of ordnance, 1861-1863.
Commanded Washington Arsenal, 1863-1866. Major, 1863, brevetted lieutenant colonel and colonel, 1865. Commanded National Armory, Springfield, Massachusetts, 1866-1881.
Promoted lieutenant colonel, 1874, colonel, 1875. Inventor electro-ballistic chronograph for determining velocity of shells, a velocimeter, a spring dynamometer, a cap-filling machine, made improvements on Springfield rifle.