The brigade was created by Major General William Rosecrans and commanded by James St. Clair Morton and George P. Buell, and served in the Stones River, Tullahoma, Chickamauga, and Chattanooga campaigns.
The men received their training in Nashville before returning to the army in time for the Battle of Stones River.
On December 31, the first day of the Battle of Stones River, the brigade was placed near army headquarters along the Nashville Pike by Rosecrans himself, in a reserve position after the Confederates collapsed the Union right.
Here, along with the Chicago Board of Trade Battery, the Pioneers played a key role in halting the high tide of the Confederate advance, allowing Rosecrans time to rally his army and eventually win the battle.
However it restored its good name in assisting the engineers in establishing the Cracker Line to relieve the city from Confederate pressure.