You’re cruising through the marshy, golden-green tidewaters of St. Helena Sound, just off the coast of Beaufort, South Carolina, and everything looks normal. It’s the Lowcountry. You see palmettos, salt marshes, and maybe a few dolphins breaking the surface of the Atlantic. Then, you see a tail. Not a fish tail. A long, furry, mammalian tail dangling from a loblolly pine. If you didn't know better, you’d think you were hallucinating or maybe stumbled onto a film set for a reboot of a 70s sci-fi flick. But no, Morgan Island is real.
It’s inhabited by over 4,000 rhesus macaques.
Most locals just call it Monkey Island. It’s one of those places that sounds like an urban legend until you’re close enough to hear the screeching. Honestly, it’s a weird bit of Southern geography that feels completely out of place. Why are thousands of primates living on a 2,000-acre marshy island in the American South? It wasn't a shipwreck. It wasn't a private eccentric billionaire’s pet project gone wrong. It was a government-mandated relocation born out of a public health crisis in the 1970s.
The weird history of how they got there
The monkeys aren't native. Obviously. They’re originally from India. Back in the late 1970s, India was the primary supplier of rhesus macaques for medical research in the United States. However, the Indian government grew increasingly concerned about the treatment of these animals and the sheer volume being exported. In 1978, India banned the export of rhesus monkeys entirely. This sent the American medical research community into a tailspin. They needed a self-sustaining, domestic breeding population to continue vaccine research and safety testing.
South Carolina stepped up. Or rather, the South Carolina Department of Natural Resources (SCDNR) entered an agreement with the U.S. Food and Drug Administration.
They chose Morgan Island because it was isolated. It provided a natural "prison" without bars. Before the monkeys arrived, the island was basically just a spot for local hunters and fishers. In 1979 and 1980, the first 1,400 monkeys were released onto the island. They didn't just survive; they thrived. The climate in the Lowcountry is surprisingly similar to parts of Southeast Asia—hot, humid, and buggy. The macaques thought they were at a resort.
Today, the population is managed by the National Institute of Allergy and Infectious Diseases (NIAID), which is part of the NIH. It’s one of the only free-ranging colonies of rhesus macaques in the United States.
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Is it actually a "secret" island?
Kinda. It’s not secret in the sense that it’s scrubbed from maps. You can see it on Google Earth. You can boat right past it. But it is strictly off-limits. You cannot set foot on the sand. If you try to dock your boat and go for a stroll, you’re going to have a very bad day involving federal law enforcement and potentially a very aggressive alpha male macaque.
There are "No Trespassing" signs posted all over the perimeter. The SCDNR and the NIH take this incredibly seriously. They aren't just protecting the monkeys from you; they’re protecting you from the monkeys. Rhesus macaques can be incredibly territorial. More importantly, they carry diseases. Specifically, many of them are carriers of the Herpes B virus. While it’s largely asymptomatic in monkeys, it can be fatal to humans.
This isn't a petting zoo. It’s a biocontainment site that happens to look like a tropical paradise.
What the monkeys actually do all day
Life on Monkey Island is pretty stratified. These animals have complex social hierarchies. They spend their time foraging, grooming each other, and navigating the internal politics of their "troops." They eat a mix of natural island vegetation and supplemental food provided by the caretakers who visit the island.
Wait, caretakers? Yeah.
A team of specialists visits regularly. They monitor the health of the colony, provide veterinary care, and ensure the population doesn't explode beyond the island's carrying capacity. About 500 to 600 monkeys are removed each year for research purposes. This is the part that gets controversial. These monkeys are used for research into everything from HIV/AIDS to vaccines for things like Ebola and, more recently, COVID-19.
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The NIH argues that the free-ranging environment on Morgan Island makes for "cleaner" and more "natural" research subjects compared to monkeys raised in small indoor cages. They get to live in a forest, swim in the creeks, and raise their young in a social group until they are needed for clinical trials.
The environmental impact of 4,000 monkeys
Nature wasn't exactly ready for this. If you put 4,000 large, active primates on a small island, the ecosystem is going to feel it. The macaques have been known to strip the bark off trees and decimate certain types of local vegetation. There have also been concerns about fecal coliform levels in the surrounding waters. Basically, monkey waste is washing into the marshes.
The SCDNR monitors the water quality closely. They have to balance the high-stakes needs of federal medical research with the fragile ecology of the South Carolina coast. It’s a weird, tense compromise.
Common misconceptions about Morgan Island
People love a good conspiracy. I’ve heard everything from "the monkeys are radioactive" to "they’re training them for space travel." None of that is true.
- Myth 1: You can see them from the mainland. Not really. You need a boat. Even then, they’re shy. They tend to hang out in the interior of the island during the heat of the day.
- Myth 2: They swim to other islands. Macaques can swim, and they actually enjoy it. However, they rarely leave Morgan Island. The currents in St. Helena Sound are brutal, and the monkeys generally know where the food is. There have been a few "escapees" over the decades, but it's rare.
- Myth 3: It’s owned by a private company. No, the land is owned by the South Carolina Department of Natural Resources, and the colony is federally managed.
How to actually see the monkeys (legally)
You can't go on the island, but you can see them from the water. If you're staying in Beaufort, Hilton Head, or Dataw Island, you can charter a boat or take a kayak tour.
Timing is everything. You want to go at low tide. When the tide is out, the monkeys often come down to the muddy banks to forage for crabs and oysters. It’s a bizarre sight. Seeing a primate crack open a South Carolina oyster is one of those things you don't forget.
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Pro-tip: Bring binoculars. A 400mm lens if you're a photographer. If you get too close with your boat, the monkeys will just retreat into the thick brush. Also, keep the engine noise down. They aren't fans of loud outboards.
Honestly, the best way to experience it is through a local guide. There are several eco-tour companies in Beaufort that know exactly where the different troops hang out. They can give you the play-by-play on the island’s history while keeping you at a safe, legal distance.
Why this place matters in 2026
We talk a lot about "ethical" research and "natural" habitats. Monkey Island is at the center of that conversation. As we look at global health threats, the demand for non-human primate research hasn't gone away, despite the push for computer modeling. The Morgan Island colony represents a middle ground—an attempt to provide a higher quality of life for research animals before they serve a scientific purpose.
Is it perfect? No. Is it weird? Absolutely.
But it’s a living, breathing part of the Lowcountry’s identity now. It’s a reminder that sometimes the most "natural" looking places are the result of very deliberate, very strange human interventions.
Actionable insights for your visit:
- Do not bring food to throw. It sounds obvious, but feeding the monkeys is a federal offense and trains them to approach boats, which leads to aggressive behavior and potential injury to the animals.
- Respect the "No Wake" zones. The marshes around the island are sensitive. Rushing in to get a photo can erode the banks that the monkeys rely on for foraging.
- Check the wind. If the wind is blowing off the island toward your boat, you’re going to smell them before you see them. It's a very distinct, pungent "zoo" smell that doesn't exactly scream "ocean breeze."
- Book a local captain. Don't try to navigate the shifting sandbars of St. Helena Sound yourself if you aren't experienced. It’s easy to get grounded, and the last place you want to be stuck is 50 yards away from a colony of 4,000 monkeys at sunset.
If you find yourself in the Beaufort area, take a morning to head out toward Morgan Island. It’s one of the few places left that feels truly "untouchable," even if it’s for a very bureaucratic reason. It’s a slice of the wild that shouldn't be there, yet somehow, it’s exactly where it needs to be.