Three questions about islands

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This is an unusual post for me because I’m asking a couple of questions.

Île Sainte-Thérèse: Does anyone live there? Is it farmland, or just cottages? Obviously you can’t get there without a boat (unless you can cross the ice in winter): what’s that like for anyone who lives there? Also: it’s quite a big piece of land, bigger than Nuns’ Island, so I wonder who it belongs to, and why you never hear about moves being made to develop it. Also: if you had a boat could you land there and walk around?

On the other side of Montreal island: Salaberry de Valleyfield. There’s a town there but the island is mostly farmland. Why didn’t this island get built up faster? It seems to be in an excellent location and you’d expect to see a much bigger town on a nice island like that.

Also: what’s the deal with Île Dorval, anyway? How can this be a municipality?