Historical marker placed at Mullan Pass.
|Elevation||5,902 ft (1,799 m)|
|Traversed by||Austin-Mullan Pass Road and Montana Rail Link (via Mullan Pass Tunnel).|
|Location||Lewis and Clark / Powell counties, Montana,
Mullan Pass is a mountain pass in the western United States, in the Rocky Mountains of Montana. It sits on the Continental Divide on the border between Powell and Lewis and Clark counties at 5,902 feet (1,799 m) above sea level. In the Helena National Forest, the pass is 13 miles (21 km) west of Helena.
The Northern Pacific Railway (NP) used the pass for its line from Logan to Garrison via Helena, built in 1883. This line was the NP's primary freight route and was also used by their secondary passenger train, the Mainstreeter. The NP also built an alternate line over Homestake Pass, which was used by their primary passenger train, the North Coast Limited. The rail line over Mullan Pass is currently operated by Montana Rail Link. The line crosses under the pass and the continental divide at 5,566 feet (1,697 m) via the 3,426-foot (0.65 mi; 1.04 km) Mullan Tunnel.
The pass was named after Lieutenant John Mullan, the U.S. Army engineer who first crossed the pass on March 22, 1854, and later supervised construction of the Mullan Road, the first road over the pass, in 1860.
On February 2, 1989, the Helena Train Wreck occurred when, during a significant cold snap, a train crew uncoupled the locomotives from a 48-car train due to mechanical issues. The air brakes failed on the cars, and the train rolled nine miles back into Helena where, at approximately 5:30 am, they collided with a parked work train and caught fire. An explosion later linked to a tank car filled with hydrogen peroxide shook the town, knocked out power, and caused extensive damage in the community, but no deaths.
In July 2009 the railroad tunnel had part of the roof collapse during renovation work designed to both widen the tunnel and make it taller. The tunnel reopened to train traffic on August 14, 2009.