Fortunately for you, there's a lot of information about that particular regiment available. For instance, Capt. George Knox Miller or Co. "A" wrote about experiences with this command during the war. Also, this message board has conducted extensive discussions about Capt. McCaa and others in the company. For instance, a link including a photographs of Capt. McCaa's uniform coat was posted.

Here are some of my notes on this company and its captains:

Company “D” of Pickens County “McCaa Rangers”

B. B. McCaa. Formerly Captain, Company “B”, 2nd Mississippi-Alabama Cavalry Battalion. Reelected August 13, 1862. Wounded near LaVergne, Tennessee, January 1, 1863; died at Murfreesboro, Tennessee, the following day.

A. B. Archibald. Promoted Captain [to rank January 2, 1863]. Captured at Shelbyville, Tennessee, June 27, 1863. Died of disease at Johnson’s Island, Ohio, February 6, 1864.

W. A. Ferguson. Captured at Shelbyville, Tennessee, June 27, 1863. Exchanged at Aiken’s Landing, Virginia, May 8, 1864. Promoted Captain [June 2, 1864,] to rank February 6, 1864. Surrendered at Columbus, Mississippi, May 17, 1865.

This company mustered at Columbus, Mississippi, November 14, 1861, as Company “B” of the 4th Mississippi Cavalry Battalion. Officers and men later served as Company “B”, 2nd Mississippi-Alabama Cavalry Battalion.