The Northern Transcon, a route operated by the BNSF Railway, traverses the most northerly route of any railroad in the western United States. This route was originally part of the Chicago, Burlington and Quincy Railroad, Northern Pacific Railway, Great Northern Railway and Spokane, Portland and Seattle Railway systems, merged into the Burlington Northern Railroad system in 1970. Route The route starts at Chicago and runs west across northern Illinois to the Mississippi River. It follows the eastern shore of the river through La Crosse and Prairie du Chien, Wisconsin before turning west again in Minneapolis and St. Paul, Minnesota to Casselton, North Dakota. From Casselton the route runs northwest to Minot, North Dakota, then west through Montana and Idaho to Spokane, Washington. In Montana, the line passes the East Gate of Glacier National Park and crosses the Two Medicine River on a high trestle. From East Glacier Park, Montana, the route continues ascending until it crests the Continental Divide at the summit of Marias Pass. The line descends down the west side of the pass for to Essex, Montana, running mostly double track on a narrow shelf, and crossing several high trestles over the Flathead River. Essex is home to the Izaak Walton Inn, which was constructed when the line was built to shelter railroad employees during the winter months. It also contains a small railyard used to store helper engines, which are used to supply additional power to freight trains crossing Marias Pass. Prior to the invention of the powerful diesel locomotives used today, longer trains often had to be split in order to make it up the pass. From Essex, the line follows the Flathead River valley to Whitefish, Montana. Located in Whitefish is a restored passenger depot/museum (also serving Amtrak). The line continues northwest to Stryker, Montana, then turns south and passes through the Flathead Tunnel as it runs west toward Sandpoint, Idaho. The line leaves the Rocky Mountains after Athol, Idaho and reaches Spokane, Washington. At Spokane the route splits into two, with one line going to Seattle, Washington and the other to Portland, Oregon. This route required construction of the Flathead Tunnel through the Rocky Mountains in Montana and the new Cascade Tunnel through the Cascade Mountains in Washington; these are the two longest railroad tunnels in the country. From St. Paul to the West Coast, this is basically the route of Amtrak's Empire Builder.