Built between 1914 and 1930, the magnificent Union Station with its spectacular Great Hall is one of Toronto's most cherished buildings. Union Station is the largest railway terminal ever built in Canada and was designated a National Historic Site in 1975. There are approximately a million square feet of space, most of it hidden from public view. Union Station is also Canada's busiest transportation facility, handling more passengers than Pearson Airport. On weekdays, 180 GO trains and 125,000 commuters pass through the station as well as 40 VIA Rail trains and 5,000 intercity passengers, over 50% of all VIA riders.
The Toronto Terminals Railway was incorporated in 1906 to build Union Station and the waterfront railway viaduct. The TTR has managed the station since it opened to the public in 1927 and continues to do so on behalf of the current owners, the City of Toronto and GO Transit.
Toronto Union Station (MP 0.0) has six east-west island platforms, each serving two tracks (for a total of twelve), located on the north side of the harbor area, below street level, connected by escalators and stairways to the circulating area behind the gates, in a subway one level below, which in turn is separated from the concourse level outside the gates, in the depot at subway level on the north side of the station, below the level of the street alongside to the north. The concourse has separate areas for Via Rail Canada and Go Transit, the Toronto area commuter system. There are also service platforms alternating with the passenger platforms, with each thus serving two tracks.
Before the collection of all main line passenger services into Via Rail Canada, Canadian Pacific and Canadian National had separate set of lines east and west of the station, so the station throats have trackage (crossovers) connecting the platform tracks to two separate sets of mainline tracks in each direction.
On the west side, the tracks are located in a trench below street level, there are three footbridges overhead, John Street tower on the north side, beneath a road bridge overhead, and a road bridge overhead. The track formation comprises two tracks on the north side, two depressed tracks in the center, and four tracks on the south side. The CN locomotive facilities (roundhouse) once stood on the south side of the line where the Skydome sits today. There is a road bridge overhead. At signal 85B, there are GO sidings on the north side, and the northernmost of the tracks on the south side crosses above the two depressed tracks to the north side. There is a road bridge overhead at which there are eight total tracks, all at the same level.
All of the tracks pass through crossovers at Bathurst Street (MP 1.1), and the CN tracks subsequently pass crossovers at Fort York (MP 1.8) and Exhibition (MP 2.0), before the tracks separate at Parkdale (MP 2.3), where the double track CP Galt Subdivision, the double track CN Weston subdivision used by trains to Sarnia via Guelph (including Amtrak's erstwhile International), and the single track CN Newmarket Subdivision used by trains to Washago and beyond, turn away to the north, while the four track CN Oakville Subdivision continues northwest along the north shore of Lake Ontario.