Interstate 15 Business (BL 15) is a business loop of Interstate 15 (I-15) in Cascade County, Montana, United States, almost entirely within Great Falls. The route links I-15 (which bypasses downtown Great Falls to the west) with the center of Great Falls. As its business loop designation implies, BL 15 terminates at I-15 (running concurrently with U.S. Route 89 [US 89] and Montana Highway 200 [MT 200] through western Great Falls) at each end. The southernmost 0.83 miles (1.34 km) of the route from the interchange with I-15 to Fox Farm Road is designated, but not signed, as Interstate 315 (I-315). I-315 is the second shortest Interstate in the country; only the unsigned I-878 is shorter.