Off the top of my head, some zoos in Canada (specially in my immediate area):
Niagara Falls Serpentarium (Niagara Falls, Ontario). I visited frequently as a child; I remember the hours were odd but they had an incredible collection from a wonderful fish tank I remember being at eye level with, and so many reptiles; not sure when it closed, but I'm guessing sometime in the mid 1980s.
Dundurn Castle Zoo (Hamilton, Ontario). Closed in the 1930s, had lions, monkeys and bison were held in the old "Cock Pit" which they used as a shelter. They also had black phase Grey Squirrels which were reportedly released when the zoo closed and there's some belief that many of Hamilton's black phase squirrels are related to this one. When a resident lion died, he was taxidermied and put on display but they aren't sure of his whereabout snow (the same goes for the head of a buffalo bull they once had in the dining room).
Hamilton Aviary (Hamilton, Ontario). Closed hopefully only temporarily due to new facilities being desperately needed; cited for mouse infestation and electrical issues. It was opened originally at Dundurn Castle sometime after the zoo closed but then closed down and moved to the old police station at Gage Park. Dundurn was a better location IMO, more spacious enclosures etc; nice variety of species in a park like setting. I somehow recall them having small monkeys in the 1980s in their Dundurn Castle location my wires are crossed and they were just at Toronto Zoo. I have somewhere a brochure with ambitious plans that would include Puffins (!) in a new facility, hope they still have plans to go ahead with it.
Steel City Safari (Hamilton, Ontario). Not a zoo per se but a convention that had exotic animals (mostly reptiles and birds) and shows featuring them. Only done for a few years' I visited in 2010, I believe.
Toronto Zoo (Riverdale Park location) (Toronto, Ontario). Closed when Toronto Zoo opened in 1974 with the resident animals moving to the Meadowvale location. Had elephants, polar bears etc. Now a farm with some old structures left behind.
Not a zoo per se but there was a bison enclosure on the Burlington Bayfront park, sometime in the 1950s. No longer in existence.
Riverside Park Zoo (Cambridge, Ontario). Once had a small zoo; unsure of species but some old structures of it remain, some of it has been demolished. May have been just a petting zoo type thing; never went. Only started going to the park after it closed.
Riverside Park Zoo (Guelph, Ontario). "In 1914, a small zoo was established near the present-day Woolwich Street entrance. Guelphites could take their kids to see lynx, coyotes, raccoons, monkeys, pheasants, deer, bears, and goats. At that time, the park was outside the city limits, so wild deer wandered in from the countryside."
Opinion | Guelph's Riverside Park — a city park like no other Not sure when it was closed
Unnamed (?) exotic game farm in Stoney Creek, Ontario. Visited with family in the 1980s, closed due to divorce. Only gate structure and old fencing remains; house burned down, and I believe the barns demolished years before. They had llamas (back then they were more exotic), bison, different deer species. Perhaps an attempt to create a zoo was started here but never came to be.
Park zoo in Paris, Ontario, or nearby area. Once had more species in this park zoo, reduced to single deer enclosure which may or may not be still open.
Bowmanville Zoo (Bowmanville, Ontario). Closed 2016. Visited only once to visit the lions featured in "The Ghost and The Darkness."
Miles Park Farm (Mississauga, Ontario)
. "By far the most popular tenant at the farm was Tootsie the elephant who originally came from Burma, and was very tame. Sadly, fire struck Miles Park Farm on Sunday, February 14, 1943 and 70 animals were lost, including Tootsie. But back to the note in the file: it recalls that Tootsie’s bones were buried on the property, and her “funeral” was attended by many saddened children from the area. Miles Park Farm remained in operation into the early 1950s. After it closed, the property was sold for development. Although we do not know where for certain, somewhere on the property the bones of Tootsie the elephant lie buried, possibly in modern Brookmede Park which is located on part of what was Miles Park Farm. Modern Dunwin Drive, as it leads north from Dundas Street, follows part of the former Miles Park Farm laneway."
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Some more info:
Other species mentioned included birds, monkeys, ostriches, horses, donkeys, camels
Mimico Beach Estates: Miles Park - Miles Road
Erie Beach Park (Fort Erie, Ontario). Once had a zoo. The zoo at the Park was a seasonal exhibition, with animals transported from the Buffalo zoo for the summer.
CEC: Closed Canadian Parks - Erie Beach Park
Shocking number, come to think of it :O