The tunnel was constructed from 1912 to 1914 by the
Chicago, Milwaukee, St. Paul and Pacific Railroad ("The Milwaukee Road") as part of its line from
Chicago to
Seattle, completed in 1909. It replaced a temporary surface line over
Snoqualmie Pass at ; this grade from Hyak to
Rockdale later became
U.S. Route 10, now the eastbound lanes of I-90. The tunnel is aligned east–west and
electrification in 1917 eliminated smoke dissipation issues. In 1980, the Milwaukee Road received approval from the
Interstate Commerce Commission to abandon its lines west of eastern Montana. On March 15, 1980, the final Milwaukee Road train passed through the tunnel. Later, the State of
Washington acquired the
right-of-way for recreational use. Today the tunnel is part of the
Iron Horse State Park rails-to-trails project. It is usually closed between November 1 through early May due to ice formations inside the tunnel. On July 5, 2011, the tunnel re-opened after 11 months of renovations. The $700,000 renovation added a layer of concrete to the walls and ceiling, a reinforced structure, and a new and improved walking surface of crushed rock. ==Gallery==