Civil War Union Brevet Brigadier General. He enlisted at the start of the Civil War in the 1st Michigan Volunteer Cavalry, being commissioned at age 24 as Captain and commander of Company I on August 21, 1861. He led his command in the Battles on the Spring of 1862 Shenandoah Valley Campaign and at the Second Battle of Bull Run, rising first to Major (September 2, 1862), then Lieutenant Colonel (November 3, 1862) of the regiment. A few months later, on January 22, 1863, he was transferred to the 9th Michigan Volunteer Cavalry to help recruit the new regiment, and serve as it's Lieutenant Colonel. The unit was mustered into Federal service in May 1863, and he participated the regiment's first field duty - the pursuit of Confederate General John Hunt Morgan's raiders in Kentucky and Ohio, in which he commanded a portion of his unit in the Battle at Bluffington Island, Ohio. After Morgan was captured, the unit joined with General Ambrose Burnside's forces in East Tennessee, where is engaged in continual scouting and skirmishing. On November 14, 1863 Lieutenant Colonel Acker was wounded at Bean's Station, Tennessee, and missed a large portion of his unit's subsequent service, but returned to lead it as a full Colonel in the Spring of 1864 (receiving his promotion on November 30, 1863). After helping to inflict a loss to the forces of General Morgan (who had escaped the Federals' hold) at Cynthiana, Kentucky, he continued to fight in lower Kentucky and Tennessee until October 1864, when the unit was detailed to General William T. Sherman's Army fighting in Georgia. He participated in the March to the Sea and the March up the Carolinas, where he finished out the war. He was brevetted Brigadier General, US Volunteers on March 13, 1865 for "gallant and soldierly conduct under all circumstances during the East Tennessee and Atlanta campaigns, especially at Morristown, East Tennessee in December 1863, at Bean Station, and for conspicuous gallantry at Cynthiana, in June 1864". After the war he became a successful Hotel Keeper, and died in Kalamazoo, Michigan in 1879.