The Great Northern Railroad built their northern transcontinental line through the Cascades Mountain Range in 1892, and reached the summit at Stevens Pass via a series of switchbacks, climbing to over 4,000 feet about sea level. In 1929, a new tunnel, the Cascade Tunnel, was completed at a length of over 7 miles, which considerably shortened the distance. With the new tunnel in play, the GN abandoned the original alignment in 1935.
These pictures show the old tunnels and snowsheds that still remain today on the original right-of-way.