Web Author's Notes:
This map shows good detail on the location of the different organizations and units at Vicksburg during the siege of that city. Interestingly, the 16th Ohio was pulled off the siege line on June 8 and sent, with General Osterhaus' Ninth Division, back to Big Black River Bridge to guard against Confederate General Joe Johnston's army which was in the area and looking for a way to attack Grant's rear and break the Union siege. It is assumed that Gen. Osterhaus' Ninth Division, including the 16th Ohio, is not shown on this map for this reason. However, it should be noted that the Osterhaus' and the 16th Ohio were important players in the First and Second Assaults on Vicksburg and participated fully in the siege until June 8.

Map by Hal Jespersen and obtained from Wikipedia.