High Quality Content by WIKIPEDIA articles! The Cascade Tunnel refers to two tunnels at Stevens Pass through the Cascade Mountains, approximately 65 miles (105 km) to the east of Everett, Washington. The first Cascade Tunnel was a 2.63-mile (4.2 km) long single track railroad, built by the Great Northern Railway in 1900 to avoid problems caused by heavy winter snowfalls on the original line that had eight Zig Zags (switchbacks). The second tunnel, a 7.79-mile (12.5 km) single-track replacement of the earlier tunnel, was put in service on January 12, 1929 and is still in operation, connecting Chelan County on its east (Berne, WA) with King County on its west (Scenic, WA). It is the longest railroad tunnel in the United States.