Curtis was a Republican Iowa Congressman and Colonel of the 2nd Iowa
Volunteer Infantry. Promoted to Brigadier General on May 17, 1861 he reported
to St. Louis and helped organize the Union forces in the area.
Given command of the Army of the Southwest on Christmas day and it’s 3 divisions, he moved to Rolla. In March 1862, the army moved into northwest Arkansas and won the battle of Pea Ridge on March 7th and 8th. After campaigning in Arkansas, Curtis earned command of the District of Missouri. Coming in political conflict with the Union Republican Governor, Hamilton Rowan Gamble, Curtis was reassigned to the Department of Kansas and Indian Territory.
During Confederate General Sterling Price’s 1864 invasion, Curtis brought his forces, the self-styled Army of the Border, east and helped defeat Price at the battle of Westport on October 23. Afterwards he was assigned to the Department of the Northwest, leading the military response to Native American uprisings against white settlers.