Rowett entered the war as captain of Company K of the 7th Illinois Ihnfantry Regiment, which is considered the first unit from Illinois to answer President Abraham Lincoln's call for volunteers. Colonel Rowett fought with distinction at the battles of Fort Donelson, Shiloh, and Corinth and fought against Confederate guerillas in northern Alabama at war's midpoint. His most notable service came at the Battle of Allatoona in Georgia on Oct. 5, 1864, when he led the defense of a pivotal Union supply depot. When the war ended he was brevetted Brigadier General of United States Volunteers.