Interstate 15 Business (Great Falls, Montana)

Interstate 15 Business is a business loop of Interstate 15 in Cascade County, Montana, United States, almost entirely within Great Falls. The route links I-15 with the center of Great Falls. As its business loop designation implies, I-15 Bus. terminates at I-15 at each end. The southernmost of the route from the interchange with I-15 to Fox Farm Road is designated, but not signed, as Interstate 315. I-315 is the second shortest Interstate in the country; only the unsigned I-878 in New York is shorter; it is also the northernmost auxiliary Interstate of I-15.

Route description

I-15 Bus. begins at I-15 exit 278 in an unincorporated area of Cascade County, a short distance southwest of Great Falls. At the trumpet interchange, US 89 and MT 200 separate from I-15 and merge with I-15 Bus. Additionally, MT 3 begins at the interchange and follows the three routes to the east. Just east of the interchange with I-15, I-15 Bus. intersects 14th Street. The Interstate Highway standard conditions come to an end a short distance to the east at an intersection with Fox Farm Road. Here, the I-315 comes to an end while I-15 Bus., US 89, MT 3, and MT 200 continue across the Missouri River into downtown Great Falls.
Within downtown, the four routes remain concurrent along 10th Avenue South to the parallel one-way couplet of 5th and 6th streets. I-15 Bus. northbound separates from US 89/MT 3/MT 200 at 6th Street, following the street northward through the city to the one-way 2nd Avenue North near the city center. I-15 Bus. turns to the west, following 2nd Avenue North to Park Street, then Park Street south to Central Avenue, where I-15 Bus. northbound rejoins the routing of I-15 Bus. southbound. Between Central Avenue and 10th Avenue South, I-15 Bus. southbound is routed along 1st Avenue North east to 5th Street South, then 5th Street South to 10th Avenue.
I-15 Bus. follows Central Avenue to the west, crossing the Missouri River once more as it exits downtown. After several intersections with local streets, I-15 Bus. terminates at I-15 exit 280. Central Avenue, however, continues westward from the exit.