The 5 worst states imo:
5. Arkansas
#33 in state population, but a very small amount of zoological facilities by my count. Little Rock is the only AZA-accredited facility but besides for that one, nothing else stands out. There's a handful of nature centers and a sanctuary for big cats and thats pretty much it. There used to be both an aquarium and safari park, but they recently closed down and were pretty poorly-reviewed by
@snowleopard. Kansas and Nebraska have a smaller population and have far more and better zoological institutions, including several of better quality, within the state.
4. West Virginia
#39 in state population. Has two non-AZA zoos in Hovatter's & Oglebay; both look small but the latter does seem alright. Also has a pretty big wildlife center with a host of native USA animals kept.
3. New Hampshire
#41 in state population. The non-AZA Living Shores Aquarium is the only official zoo/aquarium in the state. But they do have the decent-looking Squam Lakes Science Center with many native-US animals. Also some overpriced private-tour facilities and roadside-level attractions. Pretty expensive places as well.
2. Vermont
#49 in state population. There is no true zoo or aquarium, with the closest thing to qualify being the ECHO Leahy Center, a science museum with some live herps and fish. I'd at least expect the state with the most hippies to have some some sort of wild animal sanctuary, but couldn't even find any, only domestics. Between it and New Hampshire, northern New England looks like it could use a small, true zoo.
1. Wyoming
#50 in state population. Only thing resembling a zoological institution is the Teton Raptor Center. $30 for a private tour to see a few native BOPs. I doubt Wyoming could support a true zoo with its tiny population and sparseness. To its credit, there are no crappy roadsides. But as a zoo enthusiast, I can't not put in last.
Other honorable mentions: Maine, Nevada, Delaware