Wagon Masters in the Civil War

  My Ancestor, John Kerr served in Company D of the 39th Iowa Volunteer Infantry, and was detailed to serve as Wagon Master in 2. M.D., 2nd Division, XVI Corps on 26 Feb 1864 by order of BG Thomas W. Sweeney who commanded the 2nd Division at the time.  Later in November-December, 1864, he became the Wagon Master of the 2. M. Dept., 4th Division, XV Corps and served in that position for the remainder of the war.

My first question is, what does 2. M. D. stand for?  

Are there Division or Corp records that have information on the Wagon Masters of these Divisions?

On the NARA website, under Wagonmasters Serving the Union During the Civil War, there is a J. Kerr listed, but it has him serving in Washington DC rather than with his Division.  This list talks about about civilians serving as Wagon Masters, so I'm not sure if this is my John Kerr or not?

Any help would be appreciated!  Thank You!

Keith Chapman