With the outbreak of the Civil War and President
Abraham Lincoln's call for 100,000 volunteers to put down the rebellion, Sprague raised a
company of
infantry and was sent to
Camp Dennison near
Cincinnati. Upon being mustered into Federal service, he became the
captain of Company E of the
7th Ohio Infantry. While returning home on furlough in August 1861, he and a small party of fellow Buckeyes were captured in
West Virginia and held as
prisoners of war. Sprague was exchanged in January 1862 and returned to his regiment. Sprague was promoted to the rank of
brigadier general on July 30, 1864. He moved with Sherman on the
March to the Sea and then northward during the
Carolinas campaign. He commanded the brigade on its march from
Raleigh, North Carolina, through Richmond to
Washington, D.C., and participated in the
Grand Review of the Armies in May. On April 3, 1866,
President Andrew Johnson nominated Sprague for appointment to the grade of
brevet major general, to rank from March 13, 1865, and the
United States Senate confirmed the appointment on April 26, 1866. From April 1865 until September 1866, Sprague was the assistant commissioner of the
Freedmen's Bureau for the district of
Arkansas, serving under Maj. Gen.
Oliver O. Howard. He was in charge of operations in Missouri,
Kansas, and subsequently the
Indian Territory. In September 1865, he declined a
lieutenant-colonelcy in the
Regular Army and mustered out of the service. He was succeeded by
Edward O. C. Ord. ==Postbellum career==