AOP 12th Corps (Infantry) - Slocum, Williams
(The avenues at Gettysburg National Military Park follow the battle lines of commanders for which they are named. Knowing this can really help one to get oriented on the battlefield.)
Brig. Gen. Alpheus S. Williams (1810–78)
- Williams Avenue is on the southwest slope of Culp’s Hill. It connects Slocum Avenue to Wainwright Avenus in Stevens’ Knoll.
Brig. Gen. John W. Geary (1819–73)
- Geary Avenue is south of Culp’s Hill summit. It connects Spangler’s Spring to Pardee Field and Slocum Avenue near Williams.
AOP 12th Corps, 1st Division - Williams, Ruger
- Col. Archibald L. McDougall (1817-64)
- Brig. Gen. Henry H. Lockwood (1814-99)
- Brig. Gen. Thomas H. Ruger (1833-1907), until July 2, when Ruger covered for Williams who covered for Slocum. (Slocum assumed command of the Union right wing.)
- Col. Silas Colgrove (1816–1907), covering for Ruger.
Colgrove Avenue connects Baltimore Pike to Spangler’s Spring in the Culp’s Hill area.