Johnson's Island was a POW camp in Sandusky Bay,OH for CSA officer prisoners (although there were a few civilian and enlisted there,too.) I have walked the grounds and taken pictures of the gravestones of all the MS men buried there (10). Most of these have the man's unit engraved. In addition, there is a monument marker that lists 12 others from MS whose specific grave hasn't been identifed. I can Email any or all of these photos to anyone interested:
Gravestones: Col. Chas. H. Matlock- 4th Miss, Capt. W. McWhister-Co.H, 3rd Miss Inf., Capt.JN Williams-6th Miss, Lt.Fleming G.W.Coleman-7th Miss Arty, Lt. John Gobeau-Co.B,10th Miss Inf,Lt. James Lawshe-Co.C,18th Miss Cav.,Lt. Peter Mackin-Co.I, 16th Miss Inf, Lt. JW Nullins-1st Miss Inf, Pvt. WW Davis-35th Miss Inf., Albert J. Frazier-Co.H,15th Miss.
On Marker: LTC James P. Campbell, LTC AS Hamilton, LTC Samuel W. McWhorter, Capt. AB Archibald, Lt. Fleming, Lt JH Keyes,Lt. Robert K. Love, Lt. TS Maxwell, Lt Chas. Nash, Lt.Philip Nolen, Lt. Wm. Peel, C.M.Buckingham

If I can be of any assistance from here in Ohio, please don't hesitate to Email me.