Brookfield Zoo Chicago, also known as the Chicago Zoological Park, is a zoo located in the Chicago suburb of Brookfield, Illinois. It houses around 450 species of animals in an area of 216 acres (87 ha). It opened on July 1, 1934, and quickly gained international recognition for using moats and ditches instead of cages to separate animals from visitors and from other animals. The zoo was also the first in America to exhibit giant pandas, one of which (Su Lin) has been taxidermied and put on display in Chicago's Field Museum of Natural History. In 1960, Brookfield Zoo Chicago built the nation's first fully indoor dolphin exhibit, and in the 1980s, the zoo introduced Tropic World, the first fully indoor rainforest simulation and the then-largest indoor zoo exhibit in the world.

Brookfield Zoo Chicago is owned by the Forest Preserve District of Cook County and managed by the Chicago Zoological Society. The society sponsors numerous research and conservation efforts globally.

In 1919, Edith Rockefeller McCormick donated land she had received from her father as a wedding gift to the Cook County Forest Preserve District for development as a zoological garden. The district added 98 acres (400,000 m) to that plot and in 1921, the Chicago Zoological Society was established. Serious construction did not begin until 1926, after a zoo tax was approved. Construction slowed during the Great Depression, but regained momentum by late 1931. Construction went on at an increased pace and the zoo opened on July 1, 1934. By the end of September 1934, over one million people had visited the new zoo; the four millionth visitor was just two years later.

The 1950s saw the addition of a veterinary hospital, a children's zoo, and the famous central fountain. The zoo went through a decline in the 1960s until a large bond issue from the Forest Preserve District, close attention to zoo governance, and visitor services saw the zoo recreate itself as one of the nation's best. Tropic World, the then-largest indoor zoo exhibit in the world, was designed by French architect Pierre Venoa and opened in three phases (Africa, Asia, and South America) between 1982 and 1984.

During the zoo's early decades, a narrow-gauge railroad existed, which carried guests around the outer perimeter of the park from the North Gate to the old Seven Seas dolphin habitat on the park's south end. Bison lived on a small prairie on the west end of the park and could only be seen from the train, reminiscent of the Old West. The railroad was dismantled in the mid-1980s, although the pathways once used by the train still exist as roads for service vehicles, as does the North Gate station (since converted into a snack stand).

In the early 21st century, the zoo has undergone significant capital upgrades, constructing the Hamill Family Play Zoo, Regenstein Wolf Woods, butterfly tent, sheltered group catering pavilions, and the largest non-restored, hand-carved, wooden carousel in the United States. Great Bear Wilderness, a new, $27.3 million sprawling exhibit for grizzly and polar bears, opened in 2010. The interiors of several existing buildings were reconfigured into immersion exhibits, based upon ecosystems rather than by clades; these include the Living Coast (the shores of Chile and Peru), the Swamp, the Clouded Leopard Rain Forest, Desert's Edge, the African Savanna and Forest, and Australia House.

The zoo's reptile house, the first building to open in 1934, closed in 2005 and was converted into the Mary Ann McLean Conservation Leadership Center which does not display live animals, but it details the zoo's larger conservation mission. Because of the expense of constructing Great Bear Wilderness and protests from In Defense of Animals over the deaths of the zoo's African elephants, the Pachyderm House was closed for a year in 2011 for modifications and no longer exhibits elephants or river hippopotamuses.

The Children's Zoo, which opened in August 1953, was dismantled in early 2013, and a new family-based series of exhibits known as Wild Encounters opened on the site on July 1, 2015, which features a red panda, a herd of reindeer, 2 llamas, Bennet's wallabies, 22 Nigerian dwarf goats, and a free-flight parakeet aviary.

The Pachyderm building also has a pygmy hippo named 'Banana' who arrived at the zoo in May 2022 after an old female hippo passed away in June 2021.

Brookfield Zoo Chicago is also known for its majestic fountain named after the 26th president of the United States, Theodore Roosevelt. On some days, the fountain's spouting water can reach up to 60 feet high.

The zoo has been closed only five times in its history: On September 14, 2008, after damage from a weekend rainstorm; on February 2, 2011, after a major blizzard; on April 18–19, 2013, after flooding from a severe rainstorm; January 30–31, 2019, due to below-freezing temperatures; January 12, 2024, due a winter storm; and from March 19 to July 1, 2020, due to the COVID-19 pandemic.

In September 2023, the zoo received the largest private donation in the history of the zoo, $40 million, from an anonymous donor.

• Ziggy was a 6.5 ton male Asian elephant
• Binti Jua is a female western lowland gorilla
• Cookie, a Major Mitchell's cockatoo, had been part of the zoo's collection since the opening in 1934 until his death in 2016.

• Australia House: Crested pigeons, emerald tree boas, double-wattled cassowaries, emus, princess parrots, Rodrigues flying foxes, short-beaked echidnas, southern hairy-nosed wombats, western grey kangaroos, parma wallabies, prehensile-tailed skinks, Argus monitors, tawny frogmouths, and laughing kookaburras.
• Children's Zoo: Harris hawks, great horned owls, American kestrels, turkey vultures, red-tailed hawks, raccoons, ravens, chickens, goats, groundhogs, Holstein cattle, reindeer, sheep.
• Feather and Scales: Andean condors, blue poison dart frogs, double-striped thick-knees, Gambel's quails, greater roadrunners, green aracaries, boa constrictors, and sungazers.
• Perching Bird House: African pygmy-falcons, Argus monitors, Bali starlings, bay-headed tanagers, crested wood partridges, green-winged macaws, Micronesian kingfishers, paradise tanagers, tawny frogmouths, and turquoise tanagers.
• Fragile Desert: African crested porcupines, Amur leopards, bat-eared foxes, black-footed cats, caracals, meerkats, rock hyraxes, and sand cats.
• Fragile Hunters: African lions, Amur tigers, sloth bears, and snow leopards.
• Fragile Rainforest: Asian small-clawed otters, bearcats, Burmese pythons, clouded leopard, fishing cats, giant African millipedes, naked mole rats, and northern treeshrews.
• Great Bear Wilderness: American bison, bald eagles, brown bears, and polar bears.
• Habitat Africa! The Forest: African forest buffaloes, giant African millipedes, okapis, red-flanked duikers, red river hogs, and Reunion chameleons.
• Habitat Africa! The Savannah: Aardvarks, African wild dogs, common ostriches, klipspringers, reticulated giraffes, and warthogs.
• Hamill Family Play Zoo: African hedgehogs, barred tiger salamanders, mongoose lemurs, ring-tailed lemurs, Blanding's turtles, musk turtles, boa constrictors, and African cichlids.
• Hoofed Animals: Addaxes, Bactrian camels, Grant's zebras, and Grevy's zebras.
• The Living Coast: Humboldt penguins, Inca terns, gray gulls, and moray eels.
• Pachyderm House: Eastern black rhinoceroses, hippopotamuses, and South American tapirs.
• Pinniped Point: California sea lions, harbor seals.
• Regenstein Wolf Woods: Mexican wolves.
• Salt Creek Wilderness: Trumpeter swans.
• Seven Seas: Bottlenose dolphins.
• The Swamp: American alligators, alligator snapping turtles, eastern screech owls, little blue herons, North American river otter, and snowy egrets.
• Tropic World: Asian small-clawed otters, Bornean orangutans, collared mangabeys, cottontop tamarins, eastern black-and-white colobuses, giant anteaters, Geoffroy's spider monkeys, golden lion tamarins, mandrills, northern white-cheeked gibbons, pygmy hippopotamuses, sooty mangabeys, and western lowland gorillas.

Chicago cartoonist John T. McCutcheon was the president of the Chicago Zoological Society from 1921 until 1948 and oversaw the zoo's construction, opening and its early years, including helping it through the war years, when the zoo saw a decrease in attendance.

Grace Olive Wiley briefly worked as a reptile curator at the zoo in 1935.

George B. Rabb was the director from 1976 until 2003, having originally worked as a researcher and an assistant to the director.

Brookfield Zoo Chicago has a conservation project in Punta San Juan, Peru. Disney World partnered with the zoo by giving a $25,000 grant assigned specifically to the work in Punta San Juan, Peru, which helped the Chicago Zoological Society conservationists gain clearance into the highly restricted and protected area. The CZS has hired multiple people that already worked for the reserve to help build a conservation research team. Samples are taken from wildlife such as South American sea lions, Inca terns, Peruvian boobies, guanay cormorants, Grey gulls, and the endangered Humboldt penguins. The team uses the information they gathered to research the environment, observe the species, and monitor populations. Project results further knowledge about the ocean and help save endangered species. Team members also continuously have groups of children, of varying ages, go out to clean up garbage that accumulates on the beaches of Punta San Juan from the Pacific Ocean.

In 2014, revenue of Brookfield Zoo Chicago was made up by $26.6 million from admissions and guest services, $15.2 million from taxes, $11.5 million from membership dues, $11.5 million from contributions, sponsorships, and net assets released, and $1.2 million from investments and other income. Expenses in 2014 included $15.7 million for admissions and guest services, $15 million for animal collections and conservation programs, $10.7 million for care of buildings and grounds, $7.9 million for management and general, $5.9 million for public education and communications, $3.8 million for marketing and public relations, $3.4 million for fundraising, and $1.4 million for membership. Revenue totaled $66 million and spending totaled $63.8 million during 2014.

In 2010, Governor Pat Quinn granted Brookfield Zoo Chicago $15.6 million to aid repairing and remodeling many parts of the zoo. This included updating the north entrance to the zoo on 31st Street and Golfview Avenue.

The CZS has hosted several fundraising events, Wines in the Wild and Wild Wild Whirl, where they collected various donations ranging in totals from $130,000 to $1.5 million.

A total of 808 volunteers help the zoo with 74,401 community service hours which equates to $1.86 million of work.

Economic movement approaches $150 million, 2,000 jobs, 580 volunteers, and around 2.2 million visitors every year.

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  Hamill Family Play Zoo entrance
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  Rhino exhibit
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  Humboldt penguins at the Living Coast exhibit
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  Giraffes (Giraffa camelopardalis reticulata)
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  Gorilla at the zoo
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  Orangutans
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  Amur leopard
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  Peacock near pond
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  Polar bear exhibit
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  Zebra feeding on hay
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  Dolphin show
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  American alligator (Alligator mississippiensis)

• Official website