Until the advent of laws and regulations requiring the use of low sulfur coal in many places, coal customers tended to acquire their coal from the coal mines offering the lowest transportations costs, and thus coal flows tended to cluster around areas with coal mines. Longer flows included coal headed to ports for export, and specialty coals (e.g. metallurgical coal) headed to steel mills.
Even with coal flows tending to be radial flows around mines, much of the coal flowed in block trains (not yet called 'unit trains'), at least for the parts of the flows closer to the mines.
The Appalachian Coalfield is divided into a number of smaller coalfields, each of which has its own set of coal traffic flows.
Much of the anthracite was used for decades in New York City and Philadelphia, for home heating purposes. In the early decades, this made it a very lucrative traffic, and the anthracite fields were served by a number of railroads through the area, including the Delaware & Hudson, Erie, Delaware Lackawanna & Western (DL&W), Central Railroad of New Jersey, Lehigh Valley, Pennsylvania, and Reading, most of which had direct service to New York City on their own main lines, with the latter two serving Philadelphia on their main lines, with either continuing main line service to New York City (PRR, on the Northeast Corridor), or service via connecting lines (Reading).
The coalfields of western Pennsylvania are found in just about every valley west of the Susquehanna, on both sides of the eastern continental divide, and many branch lines were built to serve them, off the Pennsylvania, B&O (Sand Patch line), Western Maryland and Monongahela Railroads, including shortlines such as the Huntington & Broad Top and the narrow gauge East Broad Top. Traffic flows from these coalfields headed both east, via the PRR main line to Philadelphia (and Baltimore, via the Port Road), the B&O's Sand Patch and East End lines to Baltimore and Philadelphia, and the Western Maryland main line to Baltimore, and west, to the steel mills and factories of the industrial heartland, via the PRR main line to Pittsburgh, Cleveland, and Chicago, the B&O Chicago line to Pittsburgh and Chicago, and various others serving the Pittsburgh area.
The mines in the northern part of West Virginia are also served by branches off the Monongahela, the B&O (in this case, the West End), and the Western Maryland's line serving Elkins and the New Tygart Valley. Coal traffic flows from these mines headed north on the Monongahela to Pittsburgh, and then onward to the industrial heartland as for the western Pennsylvania mines, east on the B&O West End to Cumberland, MD, and then either east to Baltimore over the East End or (with the later closure of the direct through route in the Youghiogheny and Monongahela valleys) west to Pittsburgh and beyond over the Sand Patch line, or east on the Western Maryland main line to Baltimore.
Most of the mines in southwestern West Virginia are served by branches off the C&O main line along the New and Kanawha River valleys, with a few of the mines on these valleys served by a long branch of the New York Central. Further south, the mines are served by branches off the Virginian and branches off the north side of the Norfolk & Western Pocahontas line. Coal traffic flows off those branches served by the New York Central generally heads north or northwest to customers in the industrial heartland. Coal traffic from the C&O branches heads either west via Russell Yard to the C&O line north across the Ohio River to Columbus and Toledo, OH, or east via the New River line to tidewater at Hampton Roads. Coal traffic on the N&W branches can also head either west to the industrial heartland, via the N&W line to Columbus and its connection to Sandusky, OH, or east via the Pocahontas line to tidewater at Norfolk, VA. Since the N&W took over the Virginian, most of its coal traffic follows the N&W eastward flows, and there never were any westward flows directly on the Virginian, since its lines don't head that way.
The mines in western Virginia served by the N&W (especially the branches on the south side of the Pocahontas line) see the traffic heading the same ways on the N&W as for the branches on the north side, as described above. Some N&W branches extend further west into the Norton, VA area, with the coal traffic either heading east to the N&W main line, or exchanged to other lines for conveyance to the north and west.
Other mines in western Virginia are served by branches off the Clinchfield line, which in the 1940s and 1950s generally sent the coal northward to customers in the industrial heartland, transferring it to the C&O at Elkhorn City, KY (on the Big Sandy line), for onward conveyance. Some mines in the Big Stone Gap area, west of Norton, are served by a line that became part of the Southern Railway.
Mines in the furthest eastern part of eastern Kentucky are served by branches off the C&O Big Sandy line, the coal traffic flows from which can go either way from Russell Yard after reaching the C&O main line. At their furthest western extent, the C&O branches come into contact with the furthest eastern extent of the L&N branches southeast from Winchester, KY, and that line has other coal branches extending east from Corbin serving other mining valleys. In the 1940s and 1950s, this coal generally heads north on the L&N to Cincinnati, for onward conveyance by other lines to customers in the industrial heartland.
The development of laws and regulations requiring low sulfur coal, the almost complete cessation of the use of coal for domestic heating, and the opening of the massive Powder River Basin (a supplier of low sulfur coal) for coal mining produced vast changes in the flow of coal around the USA. Unit trains of Powder River coal may pass right by coal fields producing other varieties of coal on their way to customers (such as electricity generating stations) thousands of miles from the coal-mining region.
The rail lines serving the Powder River Basin were pioneered by the Burlington Northern in the late 1970s, but C&NW had traffic rights in the area, and eventually its rights passed to Union Pacific (because UP put up the money for construction, in the 1980s, not due to the 1995 merger), and the traffic is now shared almost evenly between BNSF and UP (except that only BNSF has access to a couple of the most northerly mines in the basin). The line in the basin itself extends north and south, and is up to four tracks wide, connecting with a BNSF line to the north, and to both BNSF and UP lines to the south.
The Powder River Basin line extends from Bridger Junction, at the south end, to Donkey Creek Junction, with connections from the ends to the nearby railroad terminals of Northport, NE and Alliance, NE (BNSF), to the east, Gillette, WY (BNSF), just west of the end of the line to the north, and South Morrill, NE, to the east (UP). All UP trains use the south end of the line, turning east at Shawnee Junction, some ten miles north of the south end of the line.
All BNSF unit coal trains are hauled by AC-traction locomotives maintained at the Alliance shop. These locomotives are attached on both the head end and rear (Distributed Power Units), and sometimes in the 'middle' of these trains.
From Gillette, the BNSF Northern Coal Route heads west on the former CB&Q Billings/Huntley line to Huntley, where it turns east on the former Northern Pacific main line to Fargo, ND, whence some trains head to Minnesota Power & Light's Clay Boswell Steam Plant at Cohasset, MN (on the former GN Grand Forks to Duluth line), or the harbor at Superior, WI (where the coal is transshipped to lake freighters for onward shipment to the Detroit Edison Power Plant at Monroe, MI), while others turn towards the Twin Cities, delivering coal to Northern States Power at Becker, MN, and Southern Minnesota Municipal Power at Becker, MN, (both to the Xcel Energy Sherburne Country Power Plant, off the former NP main south of St. Cloud) and Alliant Power at Portage, WI (on the former Milwaukee Road, transferring at St. Croix Junction, southeast of St. Paul, with run-through BNSF power).
From Donkey Creek, headed east, the former CB&Q line from Billings and Huntley, MT, leads over Crawford Hill to Alliance, where it meets the connection east from Bridger Junction.
From Alliance, the BNSF Central Coal Route heads east on the former CB&Q line from Billings and Huntley, MT, past Grand Island, NE, to Lincoln, NE, where it intersects the former CB&Q portion of the Original California Zephyr Route, used by coal trains heading for Iowa or Illinois locations, Chicago and points east, such as the Detroit Edison Monroe, MI, plant, reached via interchange in Chicago, the Water-level Route and turning north at Toledo.
Other coal trains on the BNSF Central Coal Route continue from Lincoln to Kansas City, and then over the former Frisco line to Memphis, where those, for example, headed for Plant Scherer in Georgia (two to three trains per day) continue on the former Memphis & Charleston (NS) line to Chattanooga, and then to Atlanta and the Macon area, where the plant is located; a flow to the TVA power plant at Kingston, TN takes the same route as far as Chattanooga.
From Alliance (and/or Northport), the BNSF Southern/Texas Coal Route heads south through Sterling to Brush, then southwest into Denver, taking the Colorado Joint Line south to Pueblo, where it splits (since the BN/SF merger), with loaded trains taking the Las Animas Junction route to Amarillo, and empty trains returning over Trinchera Pass. Amarillo to Denver is over the former Fort Worth & Denver, with onward routes dependent on the specific power plant forming the train's destination.
Trains on this route are typically 7,000 ft. or less in length, to fit in the sidings between Northport and Sterling, with xxx locomotives xxx
From South Morrill, UP coal trains on the Central Coal Route head east to O'Fallons, NE, where they join the Overland Route, used by those trains headed to Iowa or Illinois locations, Chicago and points east. Other trains take the diverging route at Gibbon Junction, using the Marysville line to points in Kansas, to Kansas City, and to points in Missouri and southern Illinois.
The UP Southward Coal Route take the same route as those heading eastward, diverging from the Overland Route at Gibbon Junction onto the Marysville line, and then turning south at Kansas City onto the former M-K-T line towards Oklahoma and Texas.
Colorado coal fields are in the north central part of the state, on the Craig Branch (part of David Moffatt's original Denver & Salt Lake, and in the western part of the state, southeast of Grand Junction.
This flow is a classic example of traffic optimization, providing for loaded flows of the hopper cars in both directions, during the years that SP was in the Anschutz empire (Rio Grande Industries), and the eastern connection was provided by Ed Burkhardt's Wisconsin Central. The coal flow took the former Rio Grande east from Grand Junction to Dotsero, and over Tennessee Pass, and then SP's trackage rights on the former MoPac Denver to Kansas City line as far as Herington, KS, where it transferred to the Golden State Route into Kansas City and used SP's trackage rights over the Santa Fe Transcon into the Chicago area, where a connection was made to the (then) Wisconsin Central to reach the power plant in Wisconsin. Empty hopper cars were forwarded to the source of the ore pellets in northern WI or northeastern MN, and returned loaded over the same routing, continuing beyond Grand Junction to Geneva, UT, location of a US Steel steel mill which used the pellets.
This flow ended after the UP/SP merger, when (a) UP closed the Tennessee Pass line and much of the former MoPac line across Kansas, transferring western-Colorado coal trains to the former Rio Grande Moffatt Tunnel route east of Dotsero, joining those from the Craig branch east of Orestod, and then the Julesburg connection to the Overland Route, east of Denver, and (b) the Geneva steel mill closed.
Utah coal fields are in the mountain valleys, to the south of the former Rio Grande main line over Soldier Summit, and west of Helper, served by former Rio Grande branches and by the Utah Railway.
From 1988 to 1996, coal flows from Utah to points on the SP served from Mojave traveled west over Donner Pass to Roseville, south on the SP's San Joaquin Valley line, and east over Tehachapi Pass to reach their destination at Mojave yard. In Mojave, the unit trains were split into portions for the chemical processing plant at Trona, for the cement plant at Monolith (just east of Tehachapi), and the cement plant on the Oak Creek branch, west of Mojave.
Since the UP/SP merger, the coal flows from Utah to Southern California have used the Salt Lake Route to Barstow, and trackage rights on the BNSF to Mojave, before splitting into their three portions for Trona, Monolith, and Oak Creek.
In earlier days, coal flows from the Utah coal fields to Kaiser Steel at Fontana used the Salt Lake Route to San Bernardino, where they were transferred to the Santa Fe for onward travel to Fontana on that railroad's Pasadena line.
The Appalachian Coal Field is divided into a number of smaller coalfields, each of which has its own set of of coal traffic flows.
The vast majority of the anthracite from northeastern Pennsylvania was used for domestic heating in the northeastern US, and when that market went away (it was gone by the late 1950s), so did the rail-borne coal traffic in this region. By the 1990s, most of the mines were played out, anyway. There is some activity 'mining' the leftover heaps of coil and/or spoil/slag at the mines, but little of this activity results in rail carriage of the product. What little there is is served by the Reading & Northern.
The coalfields of western Pennsylvania, much reduced in the 1990s and 2000s, are found in just about every valley west of the Susquehanna, on both sides of the eastern continental divide, and many branch lines were built to serve them, those still operating often run by RJ Corman or other shortline operators. Traffic flows from these coalfields head both east, via the Norfolk Southern (former Conrail/PRR) to Philadelphia (and Baltimore, via the Port Road), and the CSX Sand Patch and East End lines to Baltimore and Philadelphia, and west, to what remains of the steel mills and factories of the industrial heartland, via Norfolk Southern to Pittsburgh, Cleveland, and Chicago, and the CSX Chicago line to Pittsburgh and Chicago.
The mines in the northern part of West Virginia are served by branches off CSX (in this case, the West End). Coal traffic flows from these mines head east on the CSX West End to Cumberland, MD, and then either east to Baltimore over the East End or west to Pittsburgh and onward to the industrial heartland as for the western Pennsylvania mines, over the Sand Patch line.
Most of the mines in southwestern West Virginia are served by branches off the CSX main line along the New and Kanawha River valleys, with a few of the mines on these valleys served by a long branch of the former New York Central now operated by Norfolk Southern. Further south, the mines are served by Norfolk Southern branches off the former Virginian and branches off the north side of the former Norfolk & Western Pocahontas line. Coal traffic flows off those branches once served by the New York Central generally heads north or northwest to customers in the industrial heartland. Coal traffic from the CSX branches heads either west via Russell Yard to the CSX line north across the Ohio River to Columbus and Toledo, OH, or east via the New River line to tidewater at Hampton Roads. Coal traffic on the former N&W or Virginian branches can also head either west to the industrial heartland, via the NS line to Columbus and Sandusky, OH, or east via the Pocahontas line to tidewater at Norfolk, VA.
The mines in western Virginia served by the NS (especially the branches on the south side of the Pocahontas line) see the traffic heading the same ways on the NS as for the branches on the north side, as described above. Some NS branches extend further west into the Norton, VA area, with the coal traffic either heading east to the NS main line, or exchanged to other lines for conveyance to the north and west. Some coal from the Pocahontas Division heads south via Knoxville, Atlanta and Macon to power plants in southern Georgia.
Other mines in western Virginia are served by branches off the CSX Clinchfield line, which in the 1940s and 1950s generally sent the coal northward to customers in the industrial heartland, transferring it to the C&O at Elkhorn City, KY (on the Big Sandy line), for onward conveyance, but with the decline of the mills in the industrial heartland and the rise of coal-fired electrical power generation in the southeast, now sends trainload of coal south, on a daily basis, on a segment of the line which never used to see this sort of traffic desnity. Some mines in the Big Stone Gap area, west of Norton, are served by a line that became part of the Southern Railway (and thus, later, NS).
Mines in the furthest eastern part of eastern Kentucky are served by branches off the CSX Big Sandy line, the coal traffic flows from which can go either way from Russell Yard after reaching the C&O main line. At their furthest western extent, the former C&O branches come into contact with (and since the creation of CSX have been connected for through running to) the furthest eastern extent of the CSX (former L&N) branches southeast from Winchester, KY, and that line has other coal branches extending east from Corbin serving other mining valleys. In the 1940s and 1950s, this coal generally headed north on the L&N to Cincinnati, for onward conveyance by other lines to customers in the industrial heartland, but as above for the Clinchfield, more of this coal now flows south, to power generating plants in the southeast, than flows north, completely reversing the flow over the Winchester to Corbin section of the former L&N.