After garrison duty in Missouri, the regiment served in Gen. Ulysses S. Grant's Vicksburg Campaign of 1863. The regiment was one of the first ashore in Mississippi after the river crossing on April 30, 1863, and was the only Union unit to breach the defenses of Vicksburg, MS, at the Railroad Redoubt, during the general assault of May 22, 1863. In late 1863 and early 1864, the regiment participated in operations on the Texas Gulf Coast and in Louisiana. In May 1864, it was ordered to Virginia. The 22nd was one of only three regiments from Iowa to serve in Virginia, including during Gen. Philip Sheridan's Shenandoah Valley Campaign of August–November 1864. It suffered heavy losses at the Third Battle of Winchester and the Battle of Cedar Creek.