There is no single biggest zoo in America. By land, The Wilds in Ohio covers about 4,000 hectares, and the North Carolina Zoo manages 1,135 hectares. By animals, Omaha’s Henry Doorly Zoo says it has more than 33,000. By species, the San Diego Zoo leads with more than 680 species and subspecies.
Zoos quick facts
- Omaha’s Desert Dome is the world’s largest indoor desert, the zoo says.
- The Wilds in Ohio was built on land once mined for coal.
- Only 207 of the North Carolina Zoo’s 1,135 hectares are developed.
- The Safari Park opened in 1972 as the Wild Animal Park, with $1.25 tickets.
- San Diego’s Frozen Zoo stores living cells from more than 1,300 species.
America’s biggest zoos at a glance
Which is the biggest zoo in America? It sounds like an easy question, but it has several right answers. One zoo has the most land. Another has the most animals. A third has the most kinds of animals.
This guide compares the main contenders using each zoo’s own published figures. It explains what each number means, so you can decide which zoo deserves the title. Where a zoo calls itself “the largest”, the guide says that the claim is the zoo’s own.
| Measure | Biggest in this guide | Figure |
|---|---|---|
| Land | The Wilds, Ohio | About 4,000 hectares (10,000 acres) |
| Land at a traditional zoo | North Carolina Zoo | 1,135 hectares (2,805 acres) |
| Number of animals | Omaha’s Henry Doorly Zoo and Aquarium | More than 33,000 |
| Number of species | San Diego Zoo | More than 680 species and subspecies |
| Indoor desert | Omaha’s Desert Dome | About 7,800 m² (84,000 sq ft) of floor space |
Why there is no single answer
Zoos can be measured in different ways. Some people count land. Some count animals. Others count species, which means the number of different kinds of animals.
These measures do not agree. A zoo with lots of land may have fairly few animals, because each herd gets a big open space. A smaller zoo with a large aquarium may count tens of thousands of fish and insects.
So the fairest answer is to ask: biggest by what? The sections below take each measure in turn. Then you can compare the zoos side by side in the table near the end.
Biggest by land: The Wilds
The largest site in this guide is The Wilds in south-east Ohio. The Wilds says it covers more than 10,000 acres, which is about 4,000 hectares. It calls itself one of the largest conservation centres in the world.
The Wilds was built on land that was once mined for coal. Today rare animals such as Przewalski’s wild horses and giraffes roam its large open pastures.
It is not a traditional zoo with paths past animal enclosures. The Wilds describes itself as a conservation centre. It is run together with the Columbus Zoo and Aquarium.
The Columbus Zoo reports that The Wilds had 96,839 visitors in 2022. That year it recorded 225 births and hatchings. It also released 517 endangered American burying beetles into the wild.
The North Carolina Zoo
The North Carolina Zoo describes itself as “the world’s largest natural habitat zoo”. It manages 1,135 hectares (2,805 acres) of land, according to the zoo’s figures from February 2024.
Only part of that land is zoo, though. The zoo says just 207 hectares (512 acres) are developed for animal habitats and buildings. The rest is wild land that the zoo protects.
Visitors walk about 8 km (5 miles) of trails to see the animals. In February 2024 the zoo added 56 hectares (139 acres) to its Ridges Mountain Nature Preserve, taking the preserve to 171 hectares (423 acres).
San Diego Zoo Safari Park
San Diego Zoo Safari Park is in Escondido, California. The San Diego Zoo Wildlife Alliance says it covers 728 hectares (1,800 acres). That makes it one of the largest zoo parks in the country.
The Safari Park is home to more than 3,000 animals of over 293 species. It also grows more than 1.3 million plants of over 3,700 species.
A new home for elephants, the Denny Sanford Elephant Valley, opened at the Safari Park on 5 March 2026. Read more about these giants in our guide to African bush elephants.
How the Safari Park began
The Safari Park opened on 10 May 1972. The San Diego Zoo Wildlife Alliance Library says it was first called the Wild Animal Park, and an adult ticket cost just $1.25.
It was renamed San Diego Zoo Safari Park on 30 June 2010. The new name linked it more clearly to the famous zoo in the city.
The San Diego Zoo: the most species
The San Diego Zoo is a separate park from the Safari Park. It sits in Balboa Park, just north of downtown San Diego, and covers 40 hectares (100 acres).
Although it is much smaller, it holds far more kinds of animals. The San Diego Zoo Wildlife Alliance says the zoo has more than 12,000 animals of over 680 species and subspecies. That is the most species of any zoo in this guide.
The zoo is also an accredited botanical garden with more than 700,000 plants. In 2024, two giant pandas called Xin Bao and Yun Chuan arrived. Their habitat is four times larger than the old panda area.
The zoo is more than a century old. Its library says Dr Harry Wegeforth and four others held the first meeting on 2 October 1916. The zoo’s Balboa Park site was approved in 1921.
Omaha’s Henry Doorly Zoo: the most animals
Omaha’s Henry Doorly Zoo and Aquarium is in Omaha, Nebraska. The zoo says it has more than 33,000 animals. That is the highest animal count in this guide.
That number probably includes large numbers of aquarium fish and insects, so it is not a like-for-like comparison with other zoos. Still, it shows how much the zoo packs in. It covers more than 65 hectares (160 acres), including about 2.4 hectares (6 acres) of indoor animal habitats.
The zoo began in 1894 at Riverview Park, and its first animals arrived in 1895. It took the name Henry Doorly in 1963, after Margaret Hitchcock Doorly gave $750,000 in her husband’s memory.
Omaha is popular too. The zoo says it welcomed 2 million visitors in 2016 and again in 2017. In 2026 it won USA TODAY’s 10Best Readers’ Choice award for best zoo for the fourth year running.
The Desert Dome
Omaha’s most famous building is the Desert Dome. The zoo says it opened in 2002 and is the world’s largest indoor desert. It sits under the world’s largest glazed geodesic dome.
Inside, there is about 7,800 square metres (84,000 square feet) of floor space on two levels. The dome recreates three deserts. They are the Namib in southern Africa, the Red Centre of Australia and the Sonoran Desert of the USA and Mexico.
The Namib section has a sand dune about 9 metres (30 feet) high. The zoo says it is made from 300 tons of red sand. In 2026 the Desert Dome won USA TODAY’s 10Best award for best zoo exhibit.
Lied Jungle and Kingdoms of the Night
Beneath the Desert Dome is another record-breaker. The zoo describes Kingdoms of the Night, opened in 2003, as the world’s largest nocturnal exhibit. Nocturnal animals are those that are active at night.
The Lied Jungle opened in 1992 as the world’s largest indoor rainforest at the time. The zoo now calls it America’s largest indoor rainforest. It shows rainforests from South America, Asia and Africa, with gibbons, tapirs, macaws and pygmy hippos.
The Bronx Zoo
The Bronx Zoo in New York City is one of the oldest big zoos in the country. It opened on 8 November 1899, the zoo says.
It covers more than 105 hectares (260 acres) of hardwood forest. It has more than 11,000 animals of more than 640 species. That puts it close behind the San Diego Zoo for variety.
The Bronx Zoo is the flagship park of the Wildlife Conservation Society. The society runs five parks in New York.
The Columbus Zoo and Aquarium
The Columbus Zoo and Aquarium in Ohio was founded in 1927. The zoo says it welcomes more than 2 million guests a year and has more than 600 species.
It is famous for Colo, a gorilla born at the zoo, and for “Jungle” Jack Hanna. Together with The Wilds, it gives Ohio two of the biggest wildlife sites in the country.
The zoos side by side
| Zoo | Land | Animals | Species |
|---|---|---|---|
| The Wilds, Ohio | About 4,000 ha | Not given | Not given |
| North Carolina Zoo | 1,135 ha (207 ha developed) | Not given | Not given |
| San Diego Zoo Safari Park | 728 ha | 3,000+ | 293+ |
| Bronx Zoo | 105 ha | 11,000+ | 640+ |
| Omaha’s Henry Doorly Zoo | 65 ha | 33,000+ | Not given |
| San Diego Zoo | 40 ha | 12,000+ | 680+ |
The table shows how the rankings flip. The zoos with the most land do not have the most animals. The zoo with the most animals is one of the smallest by land.
Which zoo has the most visitors?
Visitor numbers are the hardest to compare. The Columbus Zoo says it gets more than 2 million guests a year, and Omaha reported 2 million visitors in 2016 and 2017.
The other zoos in this guide did not publish recent visitor totals on the pages we checked. So this guide cannot say for certain which zoo has the most visitors. Any website that names a winner should tell you where its figure comes from.
More than a day out
Big zoos do more than show animals. The San Diego Zoo Wildlife Alliance runs the Frozen Zoo, founded in 1975. It stores living cells from more than 11,500 animals of over 1,300 species at −196°C (−320°F).
The alliance says it has helped return more than 44 endangered species to the wild. At The Wilds, the release of burying beetles is part of the same kind of work.
If you visit a big zoo, look for animals you have read about, such as African lions, cheetahs, kangaroos and bald eagles. Our guide to Australian animals is a good place to start.
Three things people get wrong
Myth: the zoo with the most land has the most animals. The North Carolina Zoo manages 1,135 hectares, while Omaha covers only about 65 hectares. Yet Omaha says it has more than 33,000 animals.
Myth: more animals means more species. Omaha has the highest animal count in this guide. But the San Diego Zoo Wildlife Alliance says the San Diego Zoo has the most species and subspecies, at more than 680.
Myth: the San Diego Zoo and the Safari Park are the same place. They are two separate parks. The zoo in Balboa Park covers 40 hectares, and the Safari Park in Escondido covers 728 hectares.
Did you know? The sand dune inside Omaha’s Desert Dome is about 9 metres high and is made from 300 tons of red sand.
Try it
Rank the zoos in the comparison table three times: by land, by animals and by species. Which zoo moves the most places between your lists?
Knowledge check
Which zoo in this guide has the most species?
Show answer
The San Diego Zoo, with more than 680 species and subspecies.
What is Omaha’s Desert Dome?
Show answer
The world’s largest indoor desert, according to the zoo, with three deserts under one glass dome.
Frequently asked questions
What is the biggest zoo in America?
The answer depends on the measure. The Wilds in Ohio has the most land in this guide, Omaha has the most animals, and the San Diego Zoo has the most species.
What is the largest zoo in America by land?
The Wilds in Ohio covers about 4,000 hectares (10,000 acres). Among traditional zoos, the North Carolina Zoo manages 1,135 hectares (2,805 acres).
Which American zoo has the most animals?
Omaha’s Henry Doorly Zoo and Aquarium says it has more than 33,000 animals. That count probably includes many aquarium fish and insects.
Which American zoo has the most species?
The San Diego Zoo Wildlife Alliance says the San Diego Zoo has more than 680 species and subspecies, the most of any zoo in this guide.
Is the San Diego Zoo the same as the Safari Park?
No. The San Diego Zoo is a 40-hectare park in Balboa Park. The Safari Park is a separate 728-hectare park in Escondido, California.
How big is Omaha’s Desert Dome?
Omaha’s Desert Dome has about 7,800 square metres (84,000 square feet) of floor space on two levels. The zoo says it is the world’s largest indoor desert.
Sources
- San Diego Zoo Wildlife Alliance: Safari Park fact sheet — Safari Park land, animals, species and plants; its San Diego Zoo and alliance fact sheets and history timeline were also used
- Omaha’s Henry Doorly Zoo and Aquarium: plan your visit — land, animal count and indoor habitats; its about, Desert Dome, Lied Jungle and 10Best pages were also used
- North Carolina Zoo: more wildlife conservation lands — total and developed land (February 2024); its about page was also used
- Bronx Zoo: about — opening date, land, animals and species
- Columbus Zoo and Aquarium: about — founding, visitors and species; its report on The Wilds in 2022 was also used
- The Wilds: about — land, former coal-mined site and animals
