He also presided over the Internal Revenue Service for seven years and was a prolific author of historical non-fiction books concerning politics and general Illinois history.

Following the outbreak of the Civil War, Raum enlisted in September 1861 in the Union Army as the major of the 56th Illinois Infantry, and rose to its colonelcy in 1862.

He led the 2nd Brigade, 2nd Division, XVII Corps during the Chattanooga Campaign, and was wounded at the Battle of Missionary Ridge in November 1863.

During the 1864 Atlanta Campaign, Raum's brigade held the line of communication from Dalton to Acworth and from Kingston to Rome.

Raum was promoted to the full rank brigadier general on February 15, 1865, and served through the end of the hostilities.