Tuesday, December 20, 2022

1883+2010 BNSF/MRL/BNSF/NP Mullan Tunnel at Continental Divide

Tunnel: (Bridge Hunter)
West Portal: (Satellite)
East Portal: (Satellite)

This Northern Pacific tunnel was built in 1883 and was 3879' (1182m) long. When it was enlarged in 2009-10, it was shortened by about 400'. [BridgeHunter]

Joseph Tuch Santucci posted
Nine years, one month and thirteen days ago [that would be Nov 3, 2013], I originally posted this shot, a westing exiting Mullan tunnel and about to cross the continental divide. At this point it reaches the top of Mullan pass and will then begin its descent. From here to Missoula it is pretty much downhill all the way. Ya they used to pay me to both look at scenes like this and move these trains over this railroad.
Jim Russell: Nice photo, you can see the grade break over right at the switch.
Joseph Tuch Santucci: Jim Russell drop one notch.
clui, License: Creative Commons Attribution-NonCommercial-ShareAlike (CC BY-NC-SA)
"This tunnel at the Continental Divide at Mullan Pass, was part of the first mainline transcontinental route for the Northern Pacific Railway, and opened in 1883....The tunnel, 330 feet lower than the top of the pass, is the longest rail tunnel in Montana, even though it was shortened by 400 feet in 2009 (to 3,426 feet). When it was originally built in 1883, it was less than 13 feet wide, which provided less than three inches of room to spare for some loads. Work done in 2009 widened it by three feet, and increased its height by 5 feet, allowing more air in the tunnel, which helps to keep the high horsepower helper engines from overheating."

The 400' of length was removed from the west portal.

It is disturbing that a railroad on a 1958 map would be labeled Burlington Northern since that merger did not happen until 1970. A 1947 map has the correct names. The Mullan Tunnel is on the Northern Pacific route and the route leaving Helena to the North was the Great Northern.
1958 Butte Quad @ 250,000

"Mullan Tunnel is the longest railroad tunnel in the state of Montana standing at 3,896 feet long. To accommodate larger freight loads LRL Construction increased the whole tunnel by 5 feet in length and 3 feet in width. In total, more than 100,000 cubic yards of dirt and rock were excavated and removed from the tunnel. LRL Construction Co., Inc. was the first contractor to work on the Mullan tunnel with a perfect safety record, no accidents or incidents occurred during the work performed during normal contract hours and the 28 day collapse while working 24 hour shifts, 7 days a week."
[5' in height, not length.
I presume fixing the collapse was a separate job because if that happened during the enlargement job that would be "an incident."]

The two 250hp squirrel cage fans were removed after the tunnel was enlarged in 2009-10. [Flickr comment]
1 of 5 photos in RailfanPhotoColorado
Mullan Tunnel east portal.


  1. Are you sure that the tunnel was completed in 1883? I know that trains were using Mullen Pass in 1883 but they may have been going over it rather than through the tunnel.

    1. I cite a couple of sources that indicate the tunnel was built in 1883.