What better way to collect thoughts on this other than a zoo tier list! No, not
that Zootierliste, I mean an actual tier list, of course
This is how I consider US zoos in my mind. I've tried to keep it balanced for geographic distribution, although there's a number of sub-majors I have left off, especially on the coasts. I didn't bother with minor or obscure other than a few examples. I've left off aquariums and most other specialized facilities as that would complicate things further. The main categories considered are size, collection comprehensiveness, name recognition, and the relevance of the metropolitan areas served. A major zoo and up should take the better part of the day to go through, although many sub-majors could also be large but lacking in other categories.
World Class needs no explanation, elite are not necessarily elite in exhibition but are stand out in enough other ways that they absolutely necessitate a visit. 'Major' zoos are large, popular, recognizable, or stand out in some way, but aren't quite to the 'elite' level.
Sub-majors normally have something holding them back from being 'major' but are otherwise most of the way there and the case could be made for many to be moved up. Minor zoos are smaller facilities with less of a reach and factors like size, popularity, or recognition holding them from being 'sub-major'. Lastly 'obscure' zoos are ones that are not recognizable, large, or serving a large population center, the example being my 'home' zoo.
My rankings are probably highly debatable, and I'd be fine moving things around, this is just how things stand in my mind currently.
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