Interstate 15 Business (Great Falls, Montana)

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Interstate 15 Business

I-15 Bus. highlighted in red
Route information
Business route of I-15
Maintained by MDT
Length5.834 mi (9.389 km)
Major junctions
South end I-15 / US 89 / MT 3 / MT 200 south of Great Falls
Major intersections US 89 / MT 3 / MT 200 in Great Falls
North end I-15 / US 89 / MT 200 in Great Falls
CountryUnited States
Highway system
US 312I-315 S-315

Interstate 15 Business (I-15 Bus.) 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, I-15 Bus. terminates at I-15 (running concurrently with US Highway 89, or US 89, and Montana Highway 200, or MT 200, through western Great Falls) at each end. The southernmost 0.83 miles (1.34 km)[1] of the route from the interchange with I-15 to Fox Farm Road is designated, but not signed, as Interstate 315 (I-315).[2] I-315 is the second shortest Interstate in the country; only the unsigned I-878 is shorter.

Route description

First Baptist Church, in the city center on 2nd Avenue, March 2013

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 section that meets Interstate Highway standards comes to an end a short distance to the east at an intersection with Fox Farm Road.[3] Here, the 0.83-mile (1.34 km)[1] I-315 (designated along I-15 Bus. from I-15 to Fox Farm Road) comes to an end[4] while I-15 Bus., US 89, MT 3, and MT 200 continue across the Missouri River into downtown Great Falls.[3]

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.[3]

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.[3]

Major intersections

The entire route is in Cascade County.


I-15 / US 89 north / MT 200 west – Helena, Shelby

I-315 north / MT 3 south
Western end of I-315/US 89/MT 3/MT 200 concurrency; I-15 exit 278
Great Falls0.3350.539014th Street SouthwestInterchange
I-315 south / Fox Farm Road, 6th Street Southwest
Eastern end of I-315 concurrency

US 89 south / MT 3 south / MT 200 east (10th Avenue South) to US 87
Eastern end of US 89/MT 3/MT 200 concurrency; I-15 Bus. becomes 6th Street South (one-way street)
5.8349.389 I-15 / US 89 / MT 200 – Helena, ShelbyNorthern terminus; I-15 exit 280
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

See also


  1. ^ a b Starks, Edward (January 27, 2022). "Table 2: Auxiliary Routes of the Dwight D. Eisenhower National System of Interstate and Defense Highways". FHWA Route Log and Finder List. Federal Highway Administration. Retrieved April 9, 2023.
  2. ^ "Interstate 315 Montana". Retrieved September 24, 2007. (has pictures showing that I-315 is signed as BL 15)
  3. ^ a b c d Rand McNally (2007). "Montana" (Map). The Road Atlas '07. Chicago: Rand McNally. p. 61. § M16, N16.
  4. ^ Montana Department of Transportation (2001). Great Falls - Cascade County (PDF) (Map). Helena: Montana Department of Transportation. Retrieved September 24, 2007.

External links