Western Virginia Immediately after the Civil War began, McGinnis volunteered for service in the
11th Indiana Volunteer Infantry Regiment being raised by Col.
Lew Wallace for 3-month service. Within a month he rose from private to captain and then, on 25 April, lieutenant colonel. McGinnis and the 11th Indiana took part in Wallace's raid on
Romney, West Virginia, on 13 June 1861.
Fort Donelson and Shiloh The 3-month enlistment ran out, but the regiment was re-mustered, and on 31 August 1861, McGinnis was again made lieutenant colonel with Wallace as colonel. Due to the style of training, the regiment became known as "Wallace's Zouaves". On 3 September, Wallace was promoted to brigadier general and McGinnis became colonel of the regiment. McGinnis led the regiment during the
capture of Fort Henry and then overland toward Fort Donelson. During the
Battle of Fort Donelson, his regiment was temporarily attached to Lew Wallace's division and fought in the counterattack on the Union right. He received the praise of Lew Wallace for his actions that battle. He was in command of a brigade in the District of Eastern Arkansas. After a time of garrison duty, McGinnis was appointed to command the 1st Brigade in
Alvin P. Hovey's 12th Division of the
XIII Corps, commanded by
John A. McClernand. McGinnis's brigade was heavily engaged in the
Battle of Champion Hill and fought with distinction. During the
siege of Vicksburg, his troops occupied a length of siege lines in the center of the Union army near Fort Garrott. A bronze plaque of McGinnis is located near this spot. After the fall of Vicksburg, McGinnis fell upon a series of insignificant commands. This was possibly due to his connection with McClernand and Wallace, both of whom had become unpopular with Ulysses S. Grant and the regular army officers of the Army of the Tennessee. More significantly, McGinnis belonged to the XIII Corps, which was assigned to the Department of the Gulf. The Department of the Gulf had become relatively quiet after the fall of Vicksburg and Port Hudson. McGinnis rose to command of the 3rd Division and held that command during most of 1864. During the winter of 1864–1865 he was transferred to command the "Forces on the White River" in the Department of Arkansas. This was essentially a brigade-sized command guarding the mouth of the
White River. ==Later life==