Mullan Tunnel West Portal, Montana

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 line connected Minnesota to Puget Sound, like its chief rival, the Great Northern Railway did by a more northerly route ten years later. 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 line is now operated by Montana Rail Link, a local rail system with 900 miles of track, including this stretch between Helena and Missoula.