 After crossing into eastern Montana Territory, the regiment reached the Yellowstone River, from which point it marched downstream to Fort Union, at the rivers' mouth.From there, the regiment marched toward the Canada–US border in search of "hostile" Sioux, but returned to Fort Union empty handed.After reaching Fort Rice in central Dakota Territory, from September 10–30, 1864 four companies were sent 200 miles west to help rescue Fisk's immigrant train at Fort Dilts approximately 13 miles east of the Montana Territory border.