References:
Dyer's Compendium of the War of the Rebellion, 1908 Edition

1st REGIMENT HEAVY ARTILLERY (AFRICAN DESCENT)

Organized at Vicksburg, Miss., September 26, 1863. Attached to post of Vicksburg, District of Vicksburg, Miss., to March, 1864. Unassigned, 1st Division, U.S. Colored Troops, District of Vicksburg, to April, 1864.

SERVICE.--Post and garrison duty at Vicksburg, Miss., till April, 1864. Designation changed to 4th U. S. Colored Heavy Artillery, March 11, 1864, and to 5th U. S. Colored Heavy Artillery April 26, 1864 (which see).

2nd REGIMENT HEAVY ARTILLERY (AFRICAN DESCENT)

Organized at Natchez, Miss., September 12, 1863. Attached to post of Natchez, Miss., District of Northeast Louisiana, to January, 1864. Post of Vicksburg, District of Vicksburg, Miss., to March, 1864. District of Natchez, Miss., to April, 1864.

SERVICE.--Garrison duty at Natchez and Vicksburg, Miss., till April, 1864. Skirmish at Vidalia February 7, 1864. Designation changed to 5th U.S. Colored Heavy Artillery March 11, 1864, and to 6th U.S. Colored Heavy Artillery, April 26, 1864 (which see).