Northern Transcon
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. The two longest railroad tunnels in the country are along the Northern Transcon: the Flathead Tunnel through the Rocky Mountains in Montana and the new Cascade Tunnel through the Cascade Mountains in Washington. From St. Paul to the West Coast, this is basically the route of Amtrak's Empire Builder. But the Builder turns north in Fargo onto a BNSF secondary line to reach Grand Forks, North Dakota, while the Northern Transcon heads directly toward Minot. The Builder rejoins the Transcon main route at Minot and continues on to Seattle, though a section branches off to serve Portland, Oregon. BNSF also owns trackage with running rights in Winnipeg, Manitoba, Canada, where it has a yard operated by a switch unit and full crew. The track is maintained by a small track crew. Historical alignments in Montana
The portion of the Northern Transcon line from Columbia Falls to Libby, Montana has been significantly rerouted twice since its initial construction in 1892. Kootenai River valley
Prior to the opening of the Flathead Tunnel, trains left the modern route at Stryker, Montana and traveled northwest to Eureka, Montana, then traveled southwest along the Kootenai River and rejoined the present-day line at Jennings, located just below the Libby Dam. In 1970, the construction of the Libby Dam formed Lake Koocanusa, flooding the towns of Rexford, Montana and Waldo, British Columbia and the railroad line. This required the relocation of more than  of track between Stryker and Jennings and the building of Flathead Tunnel which, like the dam, was constructed by the US Army Corps of Engineers. Part of the original main line from Stryker to Eureka is still in use as the Mission Mountain Railroad. Before the construction of the tunnel, the Empire Builder also had a station stop in Eureka. The only visible remnants of the original route are a stub track at Jennings, where the unused original track still remains close to the current main line, and Northwest of Eureka the original mainline is now a trail that meanders over towards Lake Koocanusa, with the old right of way eventually diving into the reservoir. Haskell Pass
The alignment that travelled from Whitefish to Libby via Eureka was created in 1902 to replace a predecessor alignment over Haskell Pass, farther to the south. The pass was named for its founder, Charles Haskell, who in the winter of 1891 had set out to locate a reasonable alignment for the Great Northern railroad to take between Kalispell, Montana and the Kootenai River. Ranging as far north as the Canada–US border, Haskell's party eventually returned to Kalispell in early spring, having crossed a low notch in the Salish Mountains on the return trip. A year after the scouting trip, construction was begun on what was to be the first of three Great Northern lines through the Salish. Completed in 1892, the Haskell Pass line left the modern alignment of the route at Columbia Falls, Montana, a few miles east of Whitefish. The line travelled almost due south to Kalispell, where a branch split off the route that ran to Somers, Montana on the shore of Flathead Lake. The line travelled west from Kalispell to Marion, then alongside Little Bitteroot Lake, looping up on a high trestle over Herrig Creek, and passing through a  tunnel at the summit of Haskell Pass, emerging high on the mountains above Pleasant Valley. The line descended to the valley floor, then turned north along Island Creek, and west down Wolf Creek, to the Fisher River. The line followed the Fisher River north to the Kootenai River Valley, where it returned to the 1902–1970 alignment at Jennings. The Haskell Pass line was used only for ten years before the Kootenai River alignment opened. Shifting to the Kootenai River alignment was controversial because the new alignment was  longer than the old route, although the new route had less steep grades. Much of the Haskell Pass route was abandoned in 1902. The leg from Columbia Falls to Marion remained in use as a branch line until 1948, when it was truncated to Kalispell. When Flathead Tunnel was constructed in 1970, part of the Haskell Pass alignment along the Fisher River was recycled, namely the leg from Jennings to Tamarack siding (originally Sterling). On Haskell Pass, much of the right-of-way has been grown over, but small remnants of infrastructure and the original tunnel through the pass itself are still intact. Winter operations
Keeping the Northern Transcon open during the winter is a significant challenge, whether from snow in the Midwest and mountains, or rain in the Pacific Northwest. Heavy rains have the potential to cause mudslides along Puget Sound between Seattle and Everett and in the Nisqually, Washington area between Tacoma and Olympia. For example, in early January 2006, there were four slides between Seattle and Everett. In late January 2006 and again in early February 2006, mudslides occurred both between Seattle and Everett and around Nisqually. Heavy snow in the Rockies around Marias Pass have the potential to cause avalanches that can block the tracks. Following the clearing of a slide or an avalanche, no passenger train can run on the track for 48 hours to ensure that the slide area has stabilized, per BNSF policy. Passenger trains
Amtrak operates its Empire Builder on the corridor between La Crosse, Wisconsin and points west, though the train utilizes a more northerly route between Fargo and Minot. The Metra BNSF Line operates in the whole Chicago Subdivision, providing commuter rail service. These are the only passenger trains directly operated by BNSF via a "purchase of service agreement" with Metra. This stretch of track also hosts the Amtrak California Zephyr, the Amtrak Southwest Chief, and the Chicago-Quincy sections of  the Amtrak Illinois Service on their way to Galesburg and points west. The Northstar Line operates north of Minneapolis on the Midway and Staples Subdivisions. Also, the Seattle Subdivision hosts Amtrak Cascades as well as Sounder commuter rail trains. Subdivisions

The Northern Transcon is divided into many subdivisions. From east to west, these include:

Chicago Subdivision (Chicago, IL to Aurora, IL)
Aurora Subdivision (Aurora, IL to La Crosse, WI)
St. Croix Subdivision (La Crosse, WI to St. Croix Jct.) Joint Canadian Pacific-BNSF lines (St. Croix Jct. to St. Paul, MN)
Midway/St. Paul Subdivisions (St. Paul, MN to Minneapolis, MN)
Staples Subdivision (Minneapolis, MN to Dilworth, MN)
KO Subdivision (Dilworth, MN to Minot, ND)
Glasgow Subdivision (Minot, ND to Glasgow, MT)
Milk River Subdivision (Glasgow, MT to Havre, MT)
Hi-Line Subdivision (Havre, MT to Whitefish, MT)
Kootenai River Subdivision (Whitefish, MT to Sandpoint, ID)
Spokane Subdivision (Sandpoint, ID to Spokane, WA)

To the west of Spokane, WA (at Latah Jct, as of June 1973 to the present day), the line splits into two main routes, one using mostly the old Great Northern Railway route directly to Seattle, WA, and the other using mainly the former Spokane, Portland and Seattle Railway route, but also a large section of the former Northern Pacific Railway route, to Portland, OR via Pasco and Vancouver, WA; then it travels north to Seattle. Expedited Transcon traffic is generally routed via the direct Seattle route, and slow bulk-freight traffic is generally routed via the Spokane–Portland–Seattle route (through Vancouver, WA). The Spokane–Portland–Seattle route is mostly water level with a 1.15% maximum grade near Marshall, Washington. (Note that there is a parallel BNSF-owned route that bypasses the 1.15% grade with a maximum grade of 0.8%; they operate it directionally.) There is a 0.95% maximum grade in the Napavine, Washington area. The direct Seattle route traverses the Cascade Range at the Cascade Tunnel (Scenic and Berne, Washington); it has 2.2% ruling grades in the vicinity of the tunnel. Direct Seattle route:

Columbia River Subdivision (Spokane, WA to Wenatchee, WA)
Scenic Subdivision (Wenatchee, WA to Seattle, WA)

Portland-Seattle route:

Lakeside Subdivision (Spokane, WA to Pasco, WA)
Fallbridge Subdivision (Pasco, WA to Portland, OR)
Seattle Subdivision (Vancouver, WA to Seattle, WA)

The former Northern Pacific Railway route via Stampede Pass through Pasco and Auburn, WA to Tacoma, WA has had a checkered history. Since 1996 it has been a third route to the coast. As of 2010 it was seldom used but still in service. Stampede Pass line:

Yakima Valley Subdivision (Pasco, WA to Ellensburg, WA)
Stampede Subdivision (Ellensburg, WA to Auburn, WA)

Proposed projects
Electrification of entire routes conjunction with Canadian National and Canadian Pacific, to release diesel locomotives to relocate to Texas, Oklahoma, Vermont, New Hampshire and Maine. Grade separation of crossing with the other railroads. Reconstruction of Fargo station area. Track doubling east of Wenatchee station. See also
Southern Transcon

References

BNSF Railway lines