I did find the Preliminany Inventory of the Records of the US Army Continental Commands, 1821 - 1920. (NARA Record Group 393) in four different volumes, two of which are on CD.
Volume I, Geographical Divisions and Departments and Military (Reconstruction) Districts
Volume II, Polyonymous Successions of Commands, 1861-70 (had to look polyonymous in the dictionary! "having or known by several or many names")
Volume III, Geographical Districts and Subdistricts
Volume IV, Military Installations, 1821-81
Which volume(s) do you have?
Ken