I’ve lived in the east for a decent portion of my life, and have traveled extensively up and down the coast and other eastern states.
New York: notable zoos are Bronx, Central Park, Queens, Prospect Park, the New York Aquarium, and the Staten Island Zoo. On a visit, I would prioritize Staten Island and Bronx (especially the latter) but all of the facilities are great and depending on what you want to see, each has something to offer.
New Jersey: notable zoos are Turtle Back, Adventure Aquarium, and Cape May. The only one you’ve not visited is Turtle Back and it makes for a nice visit that should be easily combined with the Bergen County Zoo (which I’ve not been to).
Pennsylvania: there are a lot of smaller zoos in this state: Philadelphia, Lehigh Valley, Elmwood Park, Pittsburgh, Clyde Peeling’s Reptiland, and the National Aviary. You’ve been to Philly and Elmwood Park, which are two of the three that I’d recommend, the other being the National Aviary. I haven’t been to the other facilities I listed (though I plan to visit this year) except for the Pittsburgh Zoo, which I found to be a bit disappointing and a bit subpar.
Delaware: pretty much the only zoo here is Brandywine, which is extraordinarily small yet nice nonetheless.
Maryland: the National Aquarium and the Maryland Zoo are the main facilities in this state and both are nice (and can be done in the same day). There are a few more notable roadside zoos such as the Plumpton Park Zoo and the Catoctin Zoo that have rarer species, but their exhibit quality is near rock-bottom.
DC: there are two zoological facilities here, being the National Zoo and the Insect Zoo within the Museum of Natural History. The insect zoo itself is not notable, but I would recommend the museum anyways (though perhaps wait for the finished renovation of the dinosaur hall). The National Zoo is nice but is not a full day zoo, and is a bit far from the rest of the DC attractions but is easily reachable by Metro.
Virginia: the nicest trio of facilities is located in/around Norfolk, and they are the Virginia Zoo, Virginia Aquarium, and the Virginia Living Museum. I can easily do all 3 in one day but for sake of time you may just want to do the zoo and aquarium. The Living Museum is nice but is a smaller facility and is also rather expensive. A non-accredited zoo that is nice is the Metro Richmond Zoo, with a large collection and a gradually-increasing exhibit quality.
North Carolina: the zoos in this state are spread out but outstanding in quality. The North Carolina Zoo is the premier facility of course, and is fantastic all around. Sylvan Heights Bird Park is small and remote but is certainly worth a visit if you’re at all interested in birds. Duke Lemur Center is another specialist facility worth visiting, but note that you need to make a reservation in advance. The Greensboro Scuence Center is a nice zoo but a bit small, and the Carolina Raptor Center is the same way. I haven’t been to any of the North Carolina Aquariums
South Carolina: I only just visited this state for the first time but enjoyed my visit thoroughly. Riverbanks Zoo was the highlight, without a doubt, though I also enjoyed Reptile Lagoon at South of the Border. I also visited the South Carolina Aquarium which was nice but very small and imo overpriced.
Georgia: I’ve been to the two main collections in Atlanta (Zoo Atlanta and the Georgia Aquarium) and would recommend both. There are some other small facilities scattered around the state but nothing too notable as far as I’m aware.
Florida: one of the states with the most zoos in the country. Here’s a list of the ones I’ve been to:
SeaWorld Orlando
Disney's Animal Kingdom
Epcot: The Seas with Nemo and Friends
Santa Fe Teaching Zoo
St. Augustine Alligator Farm Zoological Park
Lubee Bat Conservancy
Tampa's Lowry Park Zoo
Florida Aquarium
John Pennekamp Coral Reef State Park Visitor Center and Aquarium
Butterfly Rainforest
Homosassa Springs Wildlife State Park
Busch Gardens Tampa
Jacksonville Zoo and Gardens
St. Augustine Aquarium
Lemur Conservation Foundation
Naples Zoo at Caribbean Gardens
Zoo Miami
Frost Museum of Science
Palm Beach Zoo
Lion Country Safari
Brevard Zoo
Most on this list are very high quality, with the best being DAK, Miami, Jacksonville, and Busch Gardens. The only one I wouldn’t recommend is the St. Augustine Aquarium, which is a new facility that is extremely small.
That’s all I’ve got for the east coast- sorry that I haven’t been to more of the northeast to help out. If you have questions about a specific zoo I mentioned or want me to cover more of the US, just let me know!
