In September of 1863, Union General William Rosecrans’ Army of the Cumberland met Confederate General Braxton Bragg’s Army of Tennessee at the Battle of Chickamauga. The large-scale movement of troops prior to the battle is reflected by the regional geology of the Cumberland Plateau and the Valley and Ridge. The events leading up to the battle began in the summer when Rosecrans began moving south from Murfreesboro, Tennessee with the capture of the important railroad town of Chattanooga as his objective. Rosecrans sent one of his army corps north of Chattanooga as a feint. His other two corps went to the west, ending up south of Chattanooga behind the cover of Raccoon and Sand Mountains in the Cumberland Plateau. They were now in a position to flank Bragg and cut him off from Atlanta, forcing Bragg to abandon Chattanooga without a fight.

Rosecrans then separated his three army corps and moved into the Valley and Ridge to pursue Bragg. Crittenden’s XXI Corps crossed the syncline of Lookout Mountain at the northern end at Rossville and moved south toward Lee & Gordon’s Mill. Thomas’ XIV Corps crossed Lookout Mountain through Steven’s Gap and emerged into McLemore’s Cove. McCook’s XX Corps crossed Lookout Mountain at the southern end through Winston’s Gap and Henderson’s Gap. The Confederates had moved east to the syncline of Pigeon Mountain to lay a trap for Thomas’ XIV Corps in the confined anticlinal valley of McLemore’s Cove, positioned between Lookout and Pigeon Mountains. The Confederate attack did not go as planned and the focus shifted to the more open, northern extension of the anticline.

The two armies met near Chickamauga Creek in the portion of the anticline underlain by Ordovician limestone. The Battle of Chickamauga can be related to small-scale relationships among stratigraphic units within these Ordovician rocks of the Chickamauga Supergroup. The position of the Union lines and the defense of Snodgrass Hill by General Thomas are the result of differences in topography that are directly connected to differences in lithologies. Thus, the maneuvers of armies prior to the Battle of Chickamauga and the battle itself were considerably influenced by both regional and local geology.