Although many other Kentucky State Guard units would join the Confederacy, Price and the men of "The Old Infantry" helped form the 21st Kentucky Infantry Regiment. Price enlisted as a corporal, but soon rose to the rank of captain. On February 26, 1862, he was made colonel and led the regiment through many of the major campaigns in the western theater. Price was wounded at the Battle of Kennesaw Mountain on June 27, 1864, when his regiment captured and held the Moulton and Dallas Road while being greatly outnumbered. He recovered from his wound and was subsequently assigned as post commander of Lexington, a position he held until the war ended. Price was mustered out of the U.S. volunteers on December 9, 1865. In recognition of his service and especially his leadership at Kennesaw Mountain, on January 30, 1867 (and again on March 23, 1867) President Andrew Johnson nominated Price for appointment as a brevet brigadier general of volunteers, to rank from March 13, 1865, and the United States Senate confirmed the appointment on March 28, 1867.