[3] It is part of a 60-mile (97 km) rerouting of the Great Northern Hi-Line that became a necessity due to construction of Libby Dam and subsequent creation of Lake Koocanusa.

[3] Drilling was completed on June 21, 1968 when President Lyndon B. Johnson ceremoniously triggered a final explosion from a circuit connected via telephone to the White House.

[5][6] Finishing work continued for the following two years, and the tunnel, along with the entire rerouted rail line it is a part of, opened on November 1, 1970.

An opening ceremony was held on November 7, 1970 and included the passage of the first official train through the tunnel, a 21-car passenger special carrying 1,200 area residents who were offered the opportunity to travel a circular route from Libby and back on both the new and old rail lines.

[7][8] Official records indicate that two people were killed in two separate incidents during construction, both occurring after drilling was complete.