Montana Highways

In the U.S. state of Montana, Interstate 15 continues onward from Idaho for nearly 400 miles (640 km) through the cities of Butte, Helena and Great Falls, intersecting with Interstate 90, Interstate 115 and Interstate 315. Interstate 15 reaches its northern terminus at the international border with Alberta, Canada.

Interstate 15 joins with I-90 and makes a junction with a short, one-mile (1.6 km) spur route Interstate 115 in Butte.

From Helena to Sweetgrass at the Canadian border, Interstate 15 is dedicated as a memorial highway to the First Special Service Force.