Re: Northwest 15th Ark. Inf.
I don't know anything about the Callan diary, but the Butler Center for Arkansas Studies has a copy of a typescript memoir written by James Montgomery Wilson of the 15th (Northwest)Arkansas Infantry. Most of the memoir covers Wilson's later service in the 1st Battalion (Stirman's) Arkansas Cavalry, but there are several pages devoted to his time in the 15th (NW) Ark Infantry.