Interstate 115 Montana

I-115 Montana
History
East End
West End

Overview

Butte, Montana Map
Situated at 5,538 feet above sea level, Butte is home to nearly 35,000 residents. The city and Silver Bow County form a consolidated government. I-115 provides a gateway toward the city center from the west.

Interstate 115, similar to unsigned I-315 at Great Falls to the north, comprises a short freeway spur with a lone interchange. Totaling just 1.194 miles per the MDT 2013 Route Log, I-115 doubles as the westernmost section of the Butte Business Loop for I-15/90. The business routes extend east along Iron Street to Montana Street north beyond Exit 1.

Route Information

  • East End – Butte, MT

  • West End – Butte, MT

  • Mileage – 1.19

  • Cities – Butte

  • Junctions – I-15 I-90

Source: December 31, 2018 Interstate Route Log and Finders List

I-115 Annual Average Daily Traffic (AADT)

Location Vehicles per day
I-15/90 to Excelsior Av 4,145
Excelsior Av to Washington St 3,190
Washington St to Montana St 1,898

Source: 2018 AADT – MDT’s Interactive Traffic web map

History

Construction contracts to build Interstate 115 were run concurrent with the those for the I-15/90 overlap through Butte. Contracts to build a 2.6-mile section of roadway, including all of I-115, and five bridge structures were run simultaneously with completion by September 30, 1964. Contracts to construct the western 2.7 miles of I-15/90 were scheduled to December 31, 1963, and the 5.5 mile section to the east through October 15, 1964.1

The eight-mile stretch of Interstates 15/90 was dedicated on September 24, 1964. Work on the four-lane concrete freeway started in 1960 and cost $8 million.2

Highway Guides

East End Business I-15 Business I-90 – Butte, Montana

I-115 Business I-90 East Business I-15 North at Iron Street

I-115 east at Excelsior Ave - Butte, MT

A concrete median more in line with a surface arterial separates the roadways of I-115 at Exit 1 for Excelsior Avenue. Photo taken 07/05/16.

I-115 east at Iron St - Butte, MT

The second and final reassurance marker for Interstate 115 stands east of the Excelsior Avenue underpass. Photo taken 07/05/16.

I-115 east at Iron St - Butte, MT

The speed limit drops to 35 miles per hour as the freeway portion of eastbound Business Loop I-15-90 transitions to Iron Street. Sidewalks and homes line the 0.3 mile stretch to Montana Street. Photo taken 07/05/16.

Business I-15 South Business I-90 West at I-115

Business Loop I-15/90 west at I-115 - Butte, MT

Iron Street expands into a four-lane boulevard west from Montana Street. Westbound Business Loop I-15/90 transitions into I-115 beyond the end of on-street parking at Clark Street. The first shield for Interstate 115 follows. Photo taken 07/07/16.

Excelsior Av north at I-115 - 2003

Shields for I-115 and Business Loops I-15/90 posted at the eastbound entrance ramp from Excelsior Avenue north. A folded diamond interchange joins the two roads. These Business Loop shields were replaced by 2012. Photo taken by Jeff Royston (05/17/03).

West End I-15 I-90 – Butte, Montana

I-15 North I-90 East at I-115 Business I-15 Business I-90

I-15/90 east at I-115 - Butte, MT

Traveling east from Rocker, I-15 north & I-90 east run along a ridge above parallel Silver Bow Creek to the left side ramp (Exit 124) for Interstate 115 east. Photo taken 07/05/16.

I-15/90 east at I-115 - Butte, MT

A second diagrammatic sign precedes the wye interchange (Exit 124) with I-115 east. The local exits of Montana Street and Harrison Avenue (MT 2) appear in place of Billings and Bozeman for the continuation of I-15/90 east. Photo taken 07/05/16.

I-15/90 east at I-115 - Butte, MT

Interstate 115-Business Loop I-90 east & I-15 north branch east to Iron Street in Butte as I-15/90 shifts southeast to cross Silver Bow Creek ahead of Williamsburg. The business loops return to the freeway via Harrison Avenue south at Exit 127. Photo taken 07/05/16.

I-15/90 east at I-115 - Butte, MT

Exit 124 departs for I-115 north as the roadways of I-15/90 separate. Photo taken by Steve Hanudel (05/21/06).

I-115 east at I-15/90 - Butte, MT

Confirming markers for I-115 and Business Loops I-15/90 appear just ahead of the underpass carrying motorists westward along I-15/90. The roadways of the Butte freeway spur stay separate due to the terrain on the initial stretch. Photo taken by Jeff Royston (05/17/03).

I-115 Business I-90 West Business I-15 South at I-15 I-90

I-115 west at I-15/90 - Butte, MT

I-15/90 trailblazers appearing beyond the Excelsior Avenue entrance ramp take the place of confirming markers for Business Loop I-15 south & I-90 west along I-115. Photo taken 07/05/16.

I-115 west at I-15/90 - Butte, MT

A lane drop precedes the Interstate 115 westbound merge with I-15 south & I-90 west. Photo taken 07/05/16.

I-115 west at I-15/90 - Butte, MT

Traffic from i-115 west lowers onto I-15/90, 1.5 miles ahead of the Rocker interchange. The forthcoming exit is home to a pair of truck stops. Photo taken 07/05/16.

I-115 West End Throwback

I-15/90 east at I-115 - 2006

Expansion of I-15 north & I-90 east from the Rocker interchange included the replacement of the initial sign bridge for I-115. The added eastbound lane ends a short distance ahead. Photo taken by Steve Hanudel (05/21/06).

I-15/90 east at I-115 - 2003

The subsequent diagrammatic sign for Exit 124 and I-115 was carbon copied by 2015. Photo taken by Jeff Royston (05/17/03).

Sources:

  1. Montana Highway Department. (1963). The Center line: Montana Highway Commission. Helena, MT.
  2. Montana Highway Department. (September, 1964). The Center line: Montana Highway Commission. Helena, MT.

Page updated August 28, 2019.