William Ellis joined in El Paso, he joined Company "G" as a Corporal, he was discharged as a Sergeant, I am unable to locate dates etc. Below is his regiments engagments, and officers:
Three years service
Fourth Cavalry.-Cols., T. Lyle Dickey, Martin R. M. Wallace; Lieut.-Cols., William McCullough, Martin R. M. Wallace, William L. Gibson, Majs.,William McCullough, Charles C. James, Martin R. M. Wallace Samuel M. Bowman, William L. Gibson, Mindret Wemple, Charles D. Townsend. On Sept. 26, 1861, this regiment was mustered into the U. S. service for three years and soon after took up its line of march for Springfield, where it received its arms, which were not removed from their cases, however, until the command arrived at Cairo. Upon the arrival of the regiment at Cairo it went into camp upon the highest ground that could be found, where an immense amount of labor was done by the command in the way of clearing and log rolling before a decent camp could be arranged. Very shortly after getting settled Co. C was detached and sent to the Big Muddy as a bridge guard, and Co. A was detached to serve as escort to Gen. U. S. Grant, in whose service it continued until Aug., 1863. In Dec., 1861, when the reconnoissance to Columbus, Ky., was ordered, the regiment moved with the rest of the army and became the advance body, where it kept its place during the entire, movement. It was slightly engaged at Fort Henry and then pursued the retreating Confederates toward Fort Donelson, meeting its first loss in the death of a private in Co. I. The regiment participated in the battles of Fort Donelson and Shiloh, in the movement on Corinth, then did guard duty in various places until Aug., 1863, when it was ordered to Vicksburg and remained at that place until the expiration of its term of service. In the latter part of Oct., 1864, that part of the regiment that had not reenlisted was ordered home to be mustered out. When the regiment left Cairo in Feb., 1862, it had about 1,100 men and when it came back to that point in 1864, it had 340-the latter being the number that were mustered out at Springfield in Nov. 1864.
Source: The Union Army, vol. 3
Fought at Vicksburg, MS.
Fought on 27 October 1861 at Kankakee, IL.
Fought on 06 February 1862 at Fort Henry, TN.
Fought on 15 February 1862 at Fort Donelson, TN.
Fought on 01 July 1862 at Holly Springs, MS.
Fought on 13 July 1862 at Moscow, TN.
Fought on 05 December 1862.
Fought on 05 December 1862 at Near Coffeyville.
Fought on 23 January 1863 at Near Collierville, TN.
Fought on 27 January 1863 at Centre Hills, MS.
Fought on 27 January 1863 at Near Centre Hill, MS.
Fought on 09 March 1863 at Near Colliersville, TN.
Fought on 09 May 1863.
Fought on 07 December 1863 at Independence, MO.
Fought on 04 February 1864.
Fought on 23 June 1864 at Clover Hill, MS.
Fought on 22 July 1864 at Concordia, LA.
Fought on 17 September 1864 at Near Natchez, MS.
Fought on 01 January 1865 at Franklin, TN