On the Pennsylvania Railroad, freight traffic headed from New Jersey, Philadelphia or Baltimore to the west end of the system, traveled across Pennsylvania on the four-track current-of-traffic "broad way", to Pittsburgh, and then diverged, with traffic for Chicago traveling via Crestline and Fort Wayne and traffic for St. Louis traveling via Columbus (OH) and Indianapolis. Mail traffic ran the same routings, in passenger trains prior to 1967.
The "Broad Way" route descriptions and St. Louis line
Pennsylvania Railroad (and successors) Freight Traffic from the 1940s to the 1970s
On the New York Central, freight traffic headed from New England, New York and New Jersey headed across upstate New York on the four-track, current-of-traffic, Water-level Route, to Buffalo, turning southwest through Cleveland and diverging at Berea (SW Cleveland), with traffic for Chicago heading via Toledo and traffic for St. Louis heading via Marion (OH) and Indianapolis. Mail traffic ran the same routings, in passenger trains prior to 1967.
Water-level Route descriptions and St. Louis line
The Penn Central merger (February 1, 1968) made little difference to these traffic flows (except for the downgrading of the NYC and PRR lines between Indianapolis and Chicago in favor of the former NYC routing to Elkhart via Anderson, Marion and Goshen), due to the Penn Central bankruptcy, leading eventually to Conrail (April 1, 1976). Of the other Conrail participants, only Erie(-Lackawanna) had a through route to Chicago, and no-one else had a through route to St. Louis.
Further south than these lines, the Baltimore & Ohio also had routes from Philadelphia and Baltimore (and Washington, DC) to Chicago and St. Louis, diverging at Cumberland, MD, with the former route running via Pittsburgh and the latter via Cincinnati. Mail traffic ran the same routings, in passenger trains prior to 1967.
B&O Chicago line route descriptions, Cincinnati line and St. Louis line
Over time, Conrail rationalized its route structure, combining parts of both the NYC and PRR routes between Indianapolis and St. Louis, downgrading the PRR routes between Pittsburgh and Indianapolis and between Alliance, OH, and Chicago (the Fort Wayne Line), and turning the trunk routes into a large distorted 'X', centered on Berea, OH, with Pittsburgh to Chicago traffic turning north at Alliance (onto the Cleveland Line) to go via Cleveland and then the former NYC (the Chicago Line), and Pittsburgh to St. Louis traffic diverging from this route at Berea, also on the former NYC (the Indianapolis Line and the St. Louis Line). Traffic for Texas departed the St. Louis line for the MoPac/UP at St. Elmo, IL, avoiding St. Louis. East of Harrisburg/Enola, the PRR freight routes were downgraded, and perhaps closed if they were freight-only lines, in favor of a former Reading/CNJ route via Allentown. Conrail's access to Boston used the former Boston & Albany (a subsidiary of the New York Central).
Traffic between Cincinnati and the northeast used the Dayton District, created from pieces of the former New York Central (from Cincinnati to London) and PRR (from London to Columbus), and then the former NYC Cleveland route onwards to the connection with the Indianapolis Line at Galion, OH. The PRR route from Cincinnati to London was closed.
Of course, this worked fine for the Conrail era, but the 'unmerged' lines had to make some changes to this plan.
Boston & Albany route descriptions
Conrail/NS Dayton District route descriptions
During the Conrail era, the B&O lines became part of the Chessie System, and then that Chessie System became part of CSX Transportation. Since the Chessie System had two routes from the east coast to Cincinnati, inevitably one of them became preferred and one downgraded, and ultimately, the B&O through route between Cumberland and Cincinnati was reduced to a series of coal lines in West Virginia and removed entirely in Ohio, except for a segment closer to Cincinnati, which has been operated by a regional railroad.
Traffic from New Jersey, Philadelphia or Baltimore continues to run from Pittsburgh to Cleveland, and that for Chicago continues to run on the Chicago line thereafter. Some traffic from these sources to St. Louis now continues west on the Chicago line as far as Butler, IN, where it turns onto the former Wabash line through Fort Wayne and Lafayette, IN and Decatur, IL, to get to St. Louis, while other traffic uses the former Nickel Plate through Bellevue to reach the former Wabash at Fort Wayne before joining that line for St. Louis For example, the former Mail-44, TV-3, TV-3H, and TV-20T have become 20A, 21T, 21A, and 20T, and the former TRPI has become 34N, on the Butler routing, and the former NLPI, PIEW, and PIIC have become the 10E, 11E, and 17K on the Bellevue routing.
Traffic connecting Cincinnati with the east uses the former Conrail Dayton District, now owned by NS, to connect to the NS Sandusky District to and from Bellevue Yard and connections therefrom. Trains connecting to and from the Pittsburgh area use the southeast quadrant connector at Bucyrus to connect to/from the (former) Fort Wayne Line.
NS Sandusky District route descriptions
The split left NS with no route to Boston, so some ten years later, one was cobbled together with help from Canadian Pacific (the former Delaware & Hudson) and the current owners of the former Boston & Maine, the latter in a joint venture, to form the Patriot Corridor.
Patriot Corridor route descriptions
CSX now owns and operates the Water-level Route east of Berea, OH, as well as retaining its own route from Philadelphia, Baltimore, and Washington, DC, through Pittsburgh. CSX also took over the Indianapolis Line and the St. Louis Line from Conrail, using them to connect from the Water-level Route to St. Louis, as before, but also using the Indianapolis Line to connect to the former B&O Chicago route at Greenwich, to deliver its traffic west to Chicago using that line. For example, the former (Conrail—and maybe NYC, since the NYC trade name for intermodal trains was "Trail Van") TV-7, TV-8, TV-9, TV-24, TV-77, TV-99, TV-100 and TV-304, all of which used the Water-level Route the whole way, have become CSX Q.117, Q.160, Q.119, Q.112, Q.161, Q.109, Q.110, and Q.164 over the revised routing. However, the new arrangements reduced traffic on the Indianapolis Line, since some of the traffic that used to run this way now uses the NS (former Wabash) routing through Decatur, IL, and Fort Wayne, IN.
The new arrangements also make it possible for traffic from the former B&O to head to St. Louis through the connection with the Indianapolis Line, leading to reductions in traffic via the former B&O between Cincinnati and St. Louis. For example, the former INCU and CUIN become Q.358 and Q.359. The results of this left the former B&O route without any through traffic between the end-points, and only one or two trains between Seymour, IN, and Cincinnati from the Louisville direction.
Autorack ("multi-level") trains that turned directly onto the Water-level Route at Toledo in New York Central, Penn Central, and Conrail days now take the former C&O/Hocking Valley line from Toledo to Fostoria, the former B&O main line to Greenwich, and the "Indianapolis Line" east from Greenwich to Berea, to gain their former routing east. For example, the former Conrail ML-231 and ML-276, which used the Water-level Route all the way east from Toledo, have become the CSX Q.231 and Q.276 on the revised routing.
Traffic from Cincinnati for the northeast which used to use the Dayton Line to connect to the Indianapolis Line at Galion now uses the Toledo sub. to the new Sydney Junction (southeast quadrant connector), transferring to the Indianapolis Line there. Traffic from Cincinnati to Columbus now uses this same connector and then takes the former Conrail Toledo Line south from Ridgeway, permitting the former B&O line between Cincinnati and Columbus to be downgraded and eventually sold-off.
After the new North Baltimore, OH, intermodal yard, between Deshler and Fostoria, opened in 2009, traffic between there and St. Louis has been routed east to the former C&O Toledo to Columbus line, then south to Marion, OH, where it is routed over the former ConRail "Indianapolis Line" west to St. Louis.