In the U.S. state of Montana, Interstate 15 (I-15, additionally named as the First Special Service Force Memorial Highway from Helena to the Alberta, Canada border, where it continues on into Canada retaining that designation) continues onward from Idaho for nearly 400 miles (640 km) through the cities of Butte, Helena, and Great Falls, intersecting with I-90, I-115, and I-315. I-15 reaches its northern terminus at the international border with Alberta, Canada. I-15 joins with I-90 and makes a junction with a short, one-mile (1.6 km) spur route I-115 in Butte.