Most people associate the nickname “Rock of Chickamauga” with Union Major General George H. Thomas. But the name also stuck to one of his subordinate units, the 19th U.S. Infantry, which held the Union far left at Kelly Field during the battle. The 19th’s crest clearly displays the nickname, plus a rock atop the shield itself. Here is the explanation from the Army Institute of Heraldry:
The 19th later served in the 24th Infantry Division, carrying the legacy of Chickamauga to New Guinea, the Philippines and Korea, earning three U.S., one Philippine, and two Korean Presidential Unit Citations.
Today the 19th is the training regiment at Fort Benning, GA, molding the next generation of U.S. Army infantry soldiers.