Leeper served as captain of Co. L, 3rd MSM Cavalry (redesignated from Co. B, 12th MSM Cavalry), until April 8, 1864, at which point he was dismissed from the service pursuant to Special Order 97.
Starting in 1861 Leeper was one of 99 members of the state convention that first rejected secession from the Union and then acted as a pro-Union legislative body after the sitting General Assembly evacuated Jefferson City in the early days of the war.
Starting in October 1861 Leeper served as a private in the Haw Eater Scouts for four months. During that time he organized Company B, 12th MSM Cavalry.
On April 30, 1864 -- 22 days after he was dismissed from the service -- Leeper enrolled as a private in the 68th EMM.
In August 1864 Leeper helped organize Co. A, 47th Missouri Infantry, and was elected to be captain of that company. He was denied that commission by the sitting Conservative Unionist governor.
That fall, Leeper ran for Congress, but was defeated.
After the Radicals assumed control of the governorship and statehouse that fall, Leeper -- still a private in the EMM -- was considered for appointment as brigadier general in the state militia. After that fell through, Leeper was appointed colonel in the 24th Missouri Militia. He later served in the state legislature.
Take great care in regard to any unsourced material you run across regarding Leeper. There is a bit of fiction being passed off as history regarding him (ex. -- that he really was never a colonel, and that he lied about being one). This type of tall tale telling is unfortunate. Leeper was a brutal man when he had the advantage, and a coward when he didn't. Stories don't need to be made up about him, but that doesn't stop the isolated few from having done it.