A special feature is the 2 ft (610 mm) narrow-gauge Emerson Zooline Railroad with passenger trains pulled by Chance Rides C.P.

[5] The collaborative, run by Washington University scientist Jonathan Losos, seeks to promote further understanding of the ways humans can help to preserve the varied natural environments that allow plants, animals, and microbes to survive and thrive.

The zoo initially held 51 deer and antelope, 11 buffaloes, a sacred cow, a sandhill crane, 20 prairie dogs, a dromedary camel, eagles, ducks, elk, foxes, geese, swans, rabbits, a raccoon, a China sheep, opossums, a buzzard, owls, and peafowl, among other animals.

[9] In 1972, the zoo joined the Metropolitan Zoological Park and Museum District and began to receive revenue from a public property tax of 8 cents for every $100 assessed.

In 1989, the Living World, a two-story building including classrooms, a reference library and teacher resource center, an auditorium, two exhibit halls emphasizing evolution and ecology, a large gift shop, a restaurant, and offices was built.

Phase I of River's Edge, which opened in 1999, represented Asia: featuring Asian elephants, cheetahs, dwarf mongoose, and hyenas.

In 2002, the third phase, featuring habitats of South America and Africa, opened with hippos, rhinos, warthogs, carmine bee-eaters, capybaras, and giant anteaters.

Also new that year was the Mary Ann Lee Conservation Carousel, featuring unique hand-carved wooden animals representing endangered species at the Saint Louis Zoo.

By the end of the project in 2014, the zoo had exceeded this goal by $14 million, which funded not only Grizzly Ridge or Polar Bear Point, but also Sea Lion Sound (a new and improved way of viewing the sea lions, including a walk-through tunnel), and improvements to other areas of the zoo such as Peabody Hall and River's Edge, among others.

Once completed, the new facility would feature offices and classrooms, year-round exhibits, a mixed-use development that will link the complex with the adjacent Dogtown neighborhood, and an "iconic" connection of the two sites over Interstate 64.

Most importantly, it was to shift all parking to the hospital site, freeing up roughly nine acres currently used as a surface lot for additional exhibits.

[13] In June 2022, a five-year-old eastern black rhinoceros named Moyo was permanently transferred to Alabama's Birmingham Zoo to eventually develop his own family.

[16] This $230 million, 425-acre campus will be called the St. Louis Zoo Wildcare Park and focus on endangered ungulate species and enormous habitats.

[16] The proposed initial list of animals includes Giraffe, Grevy's zebra, Greater kudu, Addax, Bongo, Roan antelope, Somali wild ass, Przewalski's horse, Scimitar-horned oryx, Waterbuck, Nile lechwe, Banteng, various Gazelle species, Southern white rhinoceros, Eland, Sable antelope, Bactrian camel, and Ostrich.

Located in the center of the zoo, Lakeside Crossing has a variety of food services and shopping destinations, and a grassy plaza where visitors can sit and relax.

River's Edge is home to a variety of animals represented from four continents: North America, Africa (Savannah and Nile), and Asia.

Until 2021, Discovery Corner also included the Emerson Children's Zoo, which had many educational features, such as the see-through slide through the otter pool and many birds, snakes, frogs, and other animals that volunteers and staff bring out for the kids to see up close.

The Children's Zoo closed in 2021 and was temporarily replaced with Dinoroarus, a walking path featuring several animatronic dinosaurs, a gift shop, and a small aquarium.

Dinoroarus closed in early 2024 to make way for the Children's Zoo's permanent successor, the Henry A. Jubel Foundation Destination Discovery, which began construction by October 2024, slated for a 2026 opening date.

The Wild is home to Grizzly Ridge, McDonnell Polar Bear Point, Fragile Forest, Jungle of the Apes, and Penguin and Puffin Coast.

The Fragile Forest features Western lowland gorilla, chimpanzee, and Sumatran orangutan in a naturalized outdoor setting.

The Bird House features birds as varied as bald eagle, rhinoceros hornbill, hyacinth macaw, burrowing owl, toco toucan, Cape thick-knee, golden pheasant, kookaburra, Mariana fruit-dove, king vulture, horned guan, superb starling, tawny frogmouth, congo peafowl, and the Guam kingfisher, which is extinct in the wild.

Other species include the Komodo dragon, green anaconda, mountain chicken, spotted turtle, false gharial, king cobra, Gila monster, frill-necked lizard, Aldabra giant tortoise, tuatara, reticulated python, tiger salamander, three-toed amphiuma, pancake tortoise, and over two dozen species of pit vipers from around the world.

The species present at Antelope Habitats are the addax, babirusa, Bactrian camel, banteng, Central Chinese goral, Grévy's zebra, lesser kudu, Nile lechwe, okapi, reticulated giraffe, Sichuan takin, Soemmerring's gazelle, Somali wild ass, Speke's gazelle, and Transcapsian urial.