Living in the Niagara Region for half my life so far, I have learned that the Niagara Region's railways are one of the most historical places in Ontario to discover.
So much has evolved over the last century. Many rail companies have changed hands.
Presently there are three primary rail companies in the Niagara Region of Ontario. They are CN, CP and Trillium.
In southwestern Ontario you have the Southern Ontario Railway, Goderich-Exeter, CP, CN, and the Essex Terminal snd also Trillium.
CN has mainline and industry trackage throughout the Niagara Region and southern Ontario. From Bayview Jct. in Hamilton, the CN Oakville Subdivision Jct's with the CN Dundas Subdivision and heads west to London and the CN Strathroy Subdivision continues on to Sarnia and through the Sarnia tunnel into Port Huron. Another rail line Jct's the CN Strathroy Subdivision at Komoka and heads to Windsor as the CN Chatham Subdivision. Back at CN Bayview Jct., the CN Oakville Subdivision goes around Hamilton harbour and heads to Niagara Falls, ON, and NY. This trackage east of Hamilton is the CN Grimsby Subdivision. From Niagara Falls ON, the CN Stamford Subdivision heads south towards CN Port Robinson and the eastern outskirts of Welland and east to Buffalo, NY area called Black Rock. CN has industries within Niagara Falls and Thorold (South). In Southwestern Ontario, CN has industry along the CN Dundas Subdivision, CN Chatham Subdivision and CN Talbot Subdivision and CN Cayuga Spur.
CP also has mainline and industrial trackage throughout Niagara and southern Ontario. They are the CP Galt Subdivision which runs out of the Toronto area and down through Campbellville and into London where the line changes over to the CP Windsor Subdivision and continues into Windsor and joins into the CN/CP Caso Subdivision. I'm not that familiar with the CP Galt Subidivision industires but I do know they have an industry at Ayr. Any other industries along this line is unknown to me. Their line into the Niagara Region is the CP Hamilton Subdivision which joins the CP Galt Subdivision at Campbellville heading down through Hamilton, Welland (Wainfleet) and down to an area east of Welland known as Brookfield. The former CP Hamilton Subdivision formerly continued on from Brookfield to Niagara Falls, NY, through Niagara Falls, ON. This Brookfield to Niagara Falls, ON portion was renamed the CP Montrose Subdivision and the portion of the trackage was abandoned and torn out for the building of Casino in Niagara Falls. The CP Montrose Subdivision ends at the south end of Niagara Falls, just north of the Jct. switch to the CP Chippawa Lead. CP as just stated, used to cross the border at Niagara Falls, but CP now crosses over to the old trackage of the CN Cayuga Subdivision to access the CN Stamford Subdivision via CN Robbins to continue east on the CN Stamford Subdivision to Buffalo, NY's Black Rock area. CP Also operates on the old CN/CP Caso Subdivision to the old area of the E&O diamond and heads south to Port Maitland on the old TH&B Dunville Spur. Though CP used to run out of Smithville on the CP Dunnville Spur, the line was abaondoned in May 2001 from Smithville to the E&O diamond area north of Dunnville about 5 miles. In Southern Ontario, CP has another line known as the CP St. Thomas Subdivision operating from Woodstock to St. Thomas. I believe the use of the St. Thomas Subdivision is for hauling frames from a plant in St. Thomas.
Trillium, operates between Port Colborne and St. Catharines on former industrial and mainline trackage through downtown Welland. Takeover of the CN Port Colborne Spur and the west side of the Macey Spur (later known as the TR Harbour Line) and Government Spur from CN began on June 25, 1997. The first train left CN WH yard in Dain City at 11:03am EST and headed south to Port Colborne. Trillium took over Welland, St. Catharines and the Thorold industrial lines on September 19, 1999. The mainline trackage I believe is leased from CN. The TR Feeder Spur sees both a daily CN train to Feeder Yard where Trillium interchanges cars. CN does this at any time, and Trillium goes to the yard in the morning to pick up their daily cars for their two trains to St. Catharines and Port Colborne. This happens btween 7:20am and 8am. I believe the St. Catharine's job starts first, as the crews begin at TR Feeder West, just down the track. They gather their cars and head up the TR Canal Spur and TR Thorold Spur to Merritton, crossing over through the cross-overs at CN Glenridge on the CN Grimsby Subdivision. Trillium has a few industries on the old NS&T trackage and one down on the old NS&T line south of the Thorold tunnel and north of Collier Road.
Their St. Thomas & Eastern 'branch' began operation in late 1998, taking over the CN Cayuga Subdivision between Delhi and St. Thomas, operating on the line once or twice a week with a handful of industries along the line. Trillium interchanges cars with CN at the yard on the CN Paynes Subdivision within St. Thomas.
Rail America's Southern Ontario Railway, formerly Railink Southern Ontario, began operations in Hamilton on December 15, 1997. Southern Ontario Railway's Hamilton operations include servicing the old CN N&NW Spur in Hamilton and switching cars in CN's former Hamilton yard which is located on the CN Oakville Subdivision just west of the Jct. to the CN Grimsby Subdivision. Southern Ontario Railway also operates between Brantford and Paris via the CN Dundas Subdivision and SOR Hagersville Subdivision from Brantford to Nanticoke. SOR has two or three industries at Nanticoke.
CSX at one time ran from the U.S. through the Windsor Tunnel up the CN Caso Subdivision through to the CSX Sarnia Subdivision at CN Fargo, then up to Sarnia through Chatham and Wallaceburg. In 2006, CSX had some aggreement with CP or CSX was using CP power to Windsor and back. In mid 2006, CSX reduced their trackage and CN bought the CSX Sarnia Subdivision from Chatham to Blenheim. CSX abandoned the CSX Sarnia Subdivision from Chatham to Wallaceburg. CSX now interchanges with CN at Sarnia.
Norfolk Southern now operates one train in Canada and it is in the Niagara Region. It is NS 369. NS 327 and 328 used to operate on the CN Paynes Subdivision for a few miles west of St. Thomas to Talbotville, the CN Talbot Subdivision from St. Thomas to London, the CN Dundas Subdivision from London to Hamilton West at Hamilton, across the 'cowpath' to the CN Oakville Subdivision, the CN Grimsby Subdivision from Hamilton to Niagara Falls and the CN Stamford Subdivision from Niagara Falls to Buffalo. Norfolk Southern ended trains 327 and 328 on December 31, 2006. Norfolk Southern used to have an Intermodal yard in Dain City, which shut down on Friday October 2, 1998. Norfolk Southern used to use the CN Cayuga Subdivision from Robbins to St. Thomas, until October 1995, when the the line west of CN Feeder West was abandoned. Norfolk Southern used the CN Canal Spur from CN Feeder South's connecting track to Dain City. Norfolk Southern still operates this one train for the present time as NS 369 into Fort Erie from Buffalo on a regular daily basis. NS used to have a train 344 and (343) which ran between Michigan and St. Thomas, vua the CN Chatham Subdivision and CN Paynes Subdivision.
Amtrak and VIA Rail operate trains through Southern Ontario, south of Toronto via the G-E Guelph, CN Dundas, CN Oakville, CN Strathroy, CN/VIA Chatham and CN Grimsby Subdivisions. Until March of 2004, the Amtrak Internation operated in Ontario, but has now ceased operations. Only a few passenger trains use the CN Grimsby Subdivision as opposed to the other lines that have passenger operations. In addtion Amtrak still has the Maple Leaf which operates between Toronto Union station to Penn station in New York state in oposing directions with 2 traine once per day.
Rail America has operated as the Goderich & Exeter, on the former CN Guelph Subdivision, CN Exeter Spur and CN Goderich Subdivision since 1992, but Rail America is the lates owner of this RR. It wasn't till 1997 or 1998 that the GEXR acquired the CN Guelph Subdivision. GEXR has running rights to 'Mac' yard (to interchange cars with CN in Brampton. GEXR operates on the CN Halton Subdivision from Georgetown eastwards as far as Mac Yard and returns westward after to home trackage. The GEXR also operates west to London, but I don't know what running rights they have on the CN Dundas Subdivision for connecting to CN for interchanging or just serving industries un tge London area on the GEXR Guelph Subdivision.
The Essex Terminal operates between Windsor and Amherstburg. They also interchange with CN at Van de Water yard in Windsor.
The Ontario Southland operates the Guelph Junction Railway (Owned by the City of Guelph) from CP Guelph Jct. in Campbellville, to Guelph, and also operates on the former CP Port Burwell Spur between Ingersoll and Tillsonberg. OSR also operates the Petro Canada spur at Clarkson, Ontario.
Finally, GO Transit operates several trains during the early morning and even hours from the Toronto area to Hamilton and back to the Toronto via the CN Oakville Subdivision and CP Hamilton Subdivision within Hamilton. They park their trains in designated tracks at Georgetown on the CN Halton Subdivision and a new Go yard I believe east of Georgetown on the CP Galt Subdivision. In 2009, GO Transit began running weekend service on the CN Grimsby Subdivision a few times a day during the summer months.