CN Kingston Subdivision

Canadian National Railway's Kingston Subdivision, or Kingston Sub for short, is a major railway line connecting Toronto with Montreal that carries the majority of CN traffic between these points. The line was originally the main trunk for the Grand Trunk Railway between these cities, although there has been some realignment of the route between these cities. The majority of the Kingston Sub runs close to the northern bank of Lake Ontario and the Saint Lawrence River.

The infrastructure consists of twin tracks, on which over 50 pieces of interlocking crossover tracks are grafted all along the subdivision. The extra length of these crossover tracks allows for high speed track interchange. Low gravity intermodal container trains are allowed to change tracks at 45 miles per hour, and VIA Rail's passenger trains, at 60, and in some areas, 90. The governing traffic control system is CTC. Since 1995, no OCS operation clearance forms need to be filled by train conductors on the Kingston Subdivision. CTC signals thus provide both permission and authorization for train movements, as is the situation with most main line operation at CN.

Just east of Newcastle, east of Toronto, the line is joined by the CP Belleville Subdivision, Canadian Pacific Railway's similar mainline route. The two remain nearly side-by-side to the east of Belleville, where the Belleville sub turns north to Smiths Falls. Sections of the Kingston Sub are no longer owned by CN. In particular, CN mainline freight traffic in the Toronto area no longer follows the Kingston Sub, and is re-directed north of the city along the York Sub. The section between Pickering Junction and Union Station in downtown Toronto has been sold to Metrolinx for GO Transit service, part of their Lakeshore East line.

Via rail of Canada operates their corridor service along the entirety of the line. VIAs Toronto-Ottawa trains runs along the line to Brockville, where it splits off and heads north. The Toronto-Montreal train runs along the whole line. In fact, many say that VIA trains run along the line more than CN freight trains. The most used station on the line is Kingston, due to Montreal, and Toronto stations being on their own subdivisions.

Stations
The 1850s Grand Trunk Railway mainline consisted of 34 stations, many of which have been removed from service or no longer exist. Lansdowne station was torn down soon after CN abandoned service to the village in 1966; CN demolished an Iroquois station in 2002.

Stations currently on the Toronto-Montréal mainline include:
 * Union Station (Toronto)
 * GO Transit (no VIA service) at Danforth, Scarborough, Eglinton in Toronto
 * Guildwood
 * Commuter stations in Rouge Hill/Pickering, Ajax and Whitby serve GO Transit; No VIA service
 * Oshawa GO Station
 * Port Hope railway station
 * Cobourg railway station
 * Brighton (not in use, now part of Memory Junction railway museum )
 * Trenton Junction railway station
 * Belleville station (Ontario)
 * Napanee railway station
 * Ernestown (not in use)
 * Kingston railway station (Ontario)
 * Kingston Outer Station (abandoned, in ruins )
 * Gananoque railway station
 * Brockville railway station
 * Prescott (not in use, now houses Grenville historical society and archives)
 * Near Morrisburg, two historic stations from The Lost Villages were relocated but did not return to service. New stations were built in Morrisburg and Long Sault in the 1950s but the train no longer stops.
 * Cornwall railway station
 * Dorval railway station (Via)
 * The line ended at Bonaventure Station, which has been replaced by Montreal Central Station.