“There was murder... there were unspeakable practices, and all of them were for the good, the bloody good, the bloody myth, for the grail, for the Tower.”
―STEPHEN KING, The Gunslinger
The history of the Tower is the history of the Ministry, and of the Capital at large. While I could take you across the country on a guided tour of magically-significant sites (by province or pentacle, as you prefer), it's not necessary to the narrative so unless we get to one of them I won't waste your time.
Where goes magic, so goes life. The rivers and fountains and streams and pools it forms draw living creatures like iron to a magnet or moths to a flame. Early man followed its pathways in his migrations across the land, settling where magic energies pooled and gave abundant life to the world. As these settlements grew, the unsuspecting geomancies of Sleeper public works and civil engineering changed the landscape, damming the flows, redirecting their courses, and forming new pools.
Where these settlements flourished the Power took on the flavour of the local culture. Borders and boundaries established by the consensus became mystically significant as the frontier faded and the idea of Canada reinforced itself. Magic gone fallow since the fall of Hyperborea was repurposed as a nation was born. For centuries the greatest source of accessible magical power within the Dominion was the Mount Royal Node. Because of this, prior to the Accord in 1982, Montreal was the eldritch capital of Canada.
It is of note that I said 'accessible' with regard to the Mount Royal Node. The greatest source of 'clean' magical energy anywhere in the Dominion is hands-down the York Sky Node, five times the size of Mount Royal. Unfortunately its position five hundred metres above the ground meant it was pretty hard to get at. Until they built the Tower.