A few comments are in order:
First of all,
@TZDugong has been to 27 of the zoos in the book, with
@Giant Eland at 59 zoos...time for an epic road trip guys in order to visit the rest!

Who has been to more than 75 of the zoos?
As
@Arizona Docent and
@Gondwana graciously pointed out, the Top 100 list that Tim and I came up with is probably "as good as anyone expected to come up with" and "it's as best a list as we can get"...to quote the two fellow ZooChatters. I can vividly recall sitting down and very rapidly coming up with approximately 95 zoos and aquariums for the book; it was honestly only the last 5 slots that were up for debate. The SeaWorld parks were locks to get into the book, as they are multi-day visits for families going on rides, and the San Diego location is a full-day visit even for someone like me who dislikes rides. The number of species is astonishing, the annual attendance numbers are outrageous, the 33,000 marine animals that have been rescued and rehabilitated is admirable and far ahead of other facilities in the book...and the millions of dollars put forth towards conservation projects dwarfs almost anyone else not called the Bronx. Whatever one thinks of Orcas in captivity, or the insane admission prices, there is no denying the amazing conservation success stories that have emerged from SeaWorld over the years.
There are loads of obvious zoos that were guarantees for the book, and as I mentioned before I think that most individuals who have already purchased a copy would likely have a very similar selection process. It wouldn't be fair to single out the facilities that barely crept into the book, but of course the USA is filled with hundreds of zoos and thus some notable establishments missed the cut. Zoo-wise I feel great about our selections, and
@Gondwana mentioned Little Rock (it's already in the book) and while Franklin Park and Blank Park are decent they are not worthy enough to bump any of the 80 zoos selected. I think that the final 80 is a perfect set.
In terms of aquariums, that was much more difficult as there are 170 public aquariums in the USA and we chose 20 to make the cut. Newport Aquarium in Kentucky, Loveland Living Planet Aquarium in Utah and Audubon Aquarium of the Americas in New Orleans are all very good but just missed out. C'est la vie!
I know that
@Arizona Docent detests theme parks and so he would rather that Tim and I had booted out Busch Gardens Tampa Bay and added in Northwest Trek Wildlife Park. Then we could have booted out Disney's Animal Kingdom and added in an obscure place in the middle of nowhere called Project Survival's Cat Haven that 99% of zoo nerds will never visit. Ha! Felines in cages along dirt pathways in the blazing California heat...add that zoo to the book!
I don't mind a little debate and I'll address my friend
@Arizona Docent in terms of a comparison between
Busch Gardens Tampa Bay and
Northwest Trek Wildlife Park. I'm the first to admit that I'm not a major fan of rollercoasters (written as one word in Canada) but when analyzing zoos one needs to look at the
whole picture and not simply focus on theme park elements.
Annual attendance: Busch Gardens is at 4.4 million while Northwest Trek is at around 220,000 and that number was even lower before they added in a $2 million playground.
Estimated visitor time: Busch Gardens is a full-day (6-7 hours) even for someone who doesn't go on rides, or a multiple-day zoo for a ride-loving family, while Northwest Trek is a 40-minute tram tour and then before the playground opened the average family spent only 2 hours at the park. I know for a fact that the playground was built specifically to get more people through the entrance and keep them for longer than the 2 hour average and it has been a rousing success.
Number of species: I'm guessing that Northwest Trek has around 30 species and it's puny in terms of the species count. There's just not a lot there, with Busch Gardens having 300 species.
@Arizona Docent have you been to Busch Gardens? The bird collection alone is at least 120 species.
Exhibits: Northwest Trek has a tram ride through a 435-acre area, plus many fenced-in slices of forest that make for excellent animal exhibits, but Busch Gardens isn't a slouch here either. The Cheetah, Tiger, African Lion, Spotted Hyena and orangutan exhibits are all pretty good, there is a 65-acre African Savanna with herds of ungulates, and the Common Hippo, Chimpanzee and Lowland Gorilla habitats are all fantastic. There are some truly superb animal habitats amidst the ice cream stands and shows.
Conservation Projects: Busch Gardens has a hefty budget in this category and easily surpasses a million dollars annually towards conservation projects.
All in all, rollercoasters aside, Busch Gardens qualified for the book without a shadow of a doubt while Northwest Trek made the 'specialist zoo' section at the back of the book. I've visited several times and it is a great wildlife park, but it wasn't even close to qualifying for a full essay.