Rhonda,

Do you think the Armstrong in question could have belonged to a Texas or Louisiana outfit? I found a couple of Texas possiblities.

Lt. George T. Armstrong, 2nd Texas Cavalry, Partisan Rangers
Capt. T.C. Armstrong, 26th Texas Cavalry

Both units are believed to have been in the area at the time. I did not check for Louisiana outfits.

Brian

P.S.
I have greatly enjoyed your very good work on Civil War Arkansas.