Here's some targets to shoot at:

Capt. Julius L Hadley 2 Mo Light Artillary, also spelled Headley, In 1864 they were in Rolla then transferred to St. Louis I beleive.

HEDLEY, Fenwick Yellowley., Brevet Captain, 1rst Lieutenant and Adjutant, 32ND IL Inf. was part of Missouri Commandry Mollus.

HEADLEY, EZEKIEL W. Commanding Sergeant 4th Regiment Provisional E.M.M was at St Joseph MO in '63 -'64, He was also a member of the 51st EMM.

FWIW
I'm not turning up much for 1864 with names that are close with rank of Capt.

John R.