Here's what little that I have on these units (as usual, from one of my *still* unfinished books):

4th Alabama Infantry Regiment of African Descent (Union Army)

Organized at Decatur, Ala., March 31, 1864. Attached to the garrison at Pulaski, Tenn. until May 1864.

Designation changed to 106th U.S. Colored Troops on May 16, 1864.

1st Alabama Infantry Regiment of African Descent,
U.S. Volunteers (Union Army)

Casualties: 8 men killed, 142 missing, and 47 wounded in the war.

Engagements: Ripley, Brice’s Crossroads, Moscow, and Waterford.

1st Alabama Siege Artillery Regiment of African Descent,
U.S. Volunteers (Union Army)

Casualties: 11 killed, 3 wounded, and 227 missing during the war.

Engagements: Fort Pillow and Holly Springs

These two regiments [1st Infantry and 1st Siege Artillery] were formed at the “contraband camp” at Corinth Mississippi, which was inhabited mostly by freed or runaway slaves from Alabama . The regiments were organized by Rev. James Alexander, who resigned as camp superintendent, to became a colonel and the commander of the new unit. Rev. Edward Pierce became its Chaplain.

This organization took place before the War Department systematized the recruitment and training of black troops. It was one of the first, and possibly the very first, units to be formed in the U.S. Army consisting of entirely of black men in the rank and file. The U.S. Army had begun to raise regiments of black freedmen in the East, however Secretary Stanton did not send Adjutant General Lorenzo Thomas to the western theater to recruit
Black troops until late March. This unit was formed several months before systematic organization began, and authorized by Washington.

The official organization date of the 1st Ala. Inf., African Descent is May 21, 1863. The initial core of the regiment seems to have been a group of sixty men, recruited to help guard the camp. By the time the regiment was fully raised, the 1st Alabama had one thousand men in its ranks. This was apparently before February 11, 1863, as that is the date that the regiment of white soldiers, that had been on duty there, was reassigned. The 1st Alabama was at that time ordered to guard the camp and a line of out-posts in the Corinth area. The regiment was attached to the 2nd Division, 16th Army Corps, Deparment of Tennessee, until November, 1863. It was then attached to the 16th Army Corps until January, 1864.

In January 1864, the garrison and the freedmen were transferred to Memphis, Tenn. At that time, it came under the control of the 1st Colored Brigade, District of Memphis, 5th Division, 16th Army Corps, and remained so until March, 1864. The designation was changed to the 55th U.S. Colored Troops on March 11, 1864. I have no information on the regiment or its assignments after that date, until it was mustered out of service on December 31, 1865..

The 1st Regiment Siege Artillery of African Descent was organized in part at the Corinth camp on June 20, 1863. It was attached to the District of Corinth, 16th Army Corps, Department of Tennessee, until November 1863, serving as a garrison for the contraband camp. Then, to the Post of Corinth, 16th Army Corps, until January, 1864. It then moved with the 1st Regiment Infantry and the camp inhabitants to Memphis. The artillery regiment was assigned to Fort Pickering, District of Memphis, Tenn., 5th Division, 16th Army Corps, until April, 1864. Four companies (A, B, C and D), were stationed at Fort Pillow, Tenn., and participated in the Massacre of Fort Pillow at that post on April 12, 1864. The designation of this regiment changed to the 6th U.S. Colored Heavy Artillery on March 11, 1864, and then to the 7th U.S. Colored Heavy Artillery on April 26, 1864. It was mustered out of service on January 12, 1866.