Here are some of those neat images from the various background doc a previous poster mentioned; an historical progression through the timeline of this site.
"Jones, Plan of Survey, 1791: made prior to the founding of the Town of York and showing the lots surveyed along the 'broken front' of the Lake Ontario shoreline before later plans of subdivision were introduced."
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"Phillpotts, Plan of York, 1818: showing the "water lots" long the broken front where the southwest corner of Yonge and Front Streets is labelled "Customs House Reserve" (the part south of The Esplanade was conveyed to John Ewart)."
"Plan 5A, c. 1840: showing part of the plan of subdivision with the portion of Lot 38 between Front Street and The Esplanade reserved for the Customs House."
"Historical Illustration, City of Toronto, 1886: the build-up of buildings and wharves to the west of the subject property and along the waterfront is shown in this illustration (Dendy, Lost Toronto, cover)."
"Archival Photograph, southwest corner of Yonge and Front Streets, 1923: showing the vacant site formerly occupied by the 1873 Customs House (demolished in 1910) with the extant Bank of Montreal to the north and the raised railway viaduct to the rear (south) that carried the tracks to Union Station (City of Toronto Archives, Fonds 1255, Item 5026)."
"Goad's Atlas, 1910 revised to 1923, Volume 1: Goad's last update shows the future site of the Dominion Public Building and, directly west (left) the new Union Station that was completed in 1919 but not officially opened until 1927 when the railway viaducts carrying the tracks were in place."
"Architectural Drawing, Dominion Public Building, 1929: showing part of the Front Street West elevation, where the west wing (right) is marked “this section not included in contract” for the initial phase of construction (City of Toronto Archives, Fonds 200, File 455)."
Streetcars! "Archival Photograph, Dominion Public Building, 1934: showing the completion of the first phase of construction with the centre and east pavilions in place (City of Toronto Archives, Series 71, Item 10254)."
"Archival Photograph, Toronto Waterfront, 1951: this view includes the rear (south) wall of the Dominion Public Building and shows its proximity to Toronto's waterfront (Toronto Public Library, Item e1-59b)."