From Stewart Sifakis' Compendium of the Confederate Armies: the 3rd Infantry Reserves was organized by the consolidation of independent companies, which had been mustered in between April 15 and July 27, 1864, on August 16, 1864. Surrendered ... at Citronelle, Alabama, on May 4, 1865. First commander was William M[cLin] Brooks.

Other information suggests that some of the companies were transferred to Co. "I" of the 63rd AL Infantry (formerly 2nd Reserves). Election of field officers was held at Selma, 5 Aug 64, but was declared "irregular, without authority, grossly improper, and entirely void," and was set aside by Major Gen'l Jones Withers and a new election ordered. However, even this new election was not held as field officers were appointed under instructions fromthe Secretary of War.

Most of the companies were assigned to Camp Cummings about 4 miles west of Mobile and were placed at various defensive points around the city, including Blakeley.