Massachusetts hides three sand islands where seals outnumber humans by a mile

The barrier islands of Monomoy

Most of Cape Cod’s summer crowds cluster around ice cream stands and mini golf. Head to the southeast elbow of the Cape, to Chatham, and you find something different.

Three barrier islands stretch into the Atlantic, and the only things on them are sand, salt marsh, and more seals than you can count. This is Monomoy National Wildlife Refuge, and the crowds haven’t found it yet.

The reason why starts with what the islands won’t let you build.

Shifting sands and 7,921 acres of wild Cape Cod

Monomoy covers 7,921 acres on the southeast tip of Cape Cod, built from barrier islands that the ocean keeps rearranging.

Three islands make up the refuge: North Monomoy, South Monomoy, and a smaller piece called Minimoy. A fourth section called the Morris Island unit sits on the mainland and is the easiest to reach on foot.

Nearly half the refuge carries federal Wilderness designation, making it the only federally designated Wilderness in all of southern New England. The islands are sand all the way down.

From fishing grounds to federal Wilderness

The Wampanoag people fished and harvested shellfish here for thousands of years before the first European settlers arrived.

The name Monomoy comes from an Algonquin word thought to mean “lookout place” or “point of land,” which tells you exactly what this geography does to the horizon.

The federal government set the area aside in 1944 to protect migrating birds, and Congress added the Wilderness designation in 1970, preserving about 3,500 acres from development.

Storms have split and rebuilt the islands repeatedly in the years since.

Up to 50,000 seals call this place home

South Monomoy Island holds the largest gray seal haul-out site on the entire U.S. Atlantic Coast. Between 30,000 and 50,000 seals use the refuge’s lands and waters across the season.

Hundreds gather on the sandbars at once, flopping in the sun and watching the boats with what looks like bored curiosity. Gray seals were once hunted to near disappearance along this coast.

Federal protection turned things around, and Monomoy is now the clearest proof of that recovery. Harbor seals also live here alongside them.

Boat out to watch hundreds of seals on the bars

Seasonal boat tours run from Chatham roughly May through October and bring you close to the beaches where the seals rest in piles.

The best time to go is at low tide, when the sandbars break the surface and the seals haul themselves out to dry and warm up. High tide pushes them back into the water, and you’ll see far fewer.

Tours run from a couple of different outfitters in Chatham, so check the official website for current schedules and booking. Most tours last about 90 minutes.

More than 40 shorebird species pass through each year

Monomoy sits directly on the Atlantic Flyway, the great migratory corridor that runs along the Eastern Seaboard, and the birds know it.

More than 40 species of shorebirds move through the refuge each year, and the offshore islands host at least 25 species of seabird, shorebird, waterfowl, and colonial waterbird that actually nest here.

In 2022, the common tern colony topped 17,000 nesting pairs, the largest on the Atlantic seaboard. The refuge has been recognized as a Globally Important Bird Area, which is not a designation they hand out casually.

Five threatened species nest right here on the sand

Monomoy holds the highest concentration of nesting piping plovers in New England, and five species at the refuge carry federal protection under the Endangered Species Act.

That list includes the piping plover, roseate tern, red knot, northeastern beach tiger beetle, and sea beach amaranth.

The red knot is a long-distance migrant that makes the refuge a critical stop during its spring and fall journeys.

Walk the beach slowly in nesting season and you’ll also spot snowy egrets, willets, least terns, and American oystercatchers working the tide line.

Ancient creatures blanket the beach in May and June

Horseshoe crabs are older than the dinosaurs, and every spring they crawl up onto Monomoy’s beaches in some of the highest concentrations in Massachusetts.

Spawning peaks in May and June, when the crabs come up with the high tides to lay their eggs by the millions in the wet sand.

Those eggs feed thousands of migrating shorebirds, including the red knot, which times its entire northward migration to arrive when the eggs are ready.

A single horseshoe crab spawn can refuel a bird for thousands more miles of flight.

Walk the Morris Island trail for free, any time of year

You don’t need a boat to get a feel for Monomoy. The Morris Island trail starts at 30 Wikis Way in Chatham and winds through pine forest, salt marsh, dunes, and tidal flats before dropping you onto the beach.

Interpretive signs along the way explain the habitats and the wildlife that depends on them. The trail is free and open year-round, which makes it one of the better deals on the Cape.

Pay attention to the tides, though. Much of the beach section floods at high water, and you can find yourself cut off if you don’t plan ahead.

Great whites follow the seals to Chatham’s waters

All those seals have drawn something else to the Chatham area.

Great white sharks now patrol the waters around Monomoy regularly, following one of the densest prey populations on the East Coast.

Researchers use the area as an active study site, tagging sharks and tracking their movements through the season.

The seals, the sharks, and the shorebirds are all threads in the same coastal food web, each dependent on the others.

Standing on the beach watching the seals piled on a sandbar, you’re looking at an entire ecosystem running on its own terms.

A lighthouse built in 1849 still stands on the far island

The Monomoy Point Light sits at the southern tip of South Monomoy Island, its cast-iron tower built in 1849 to replace an earlier light from 1823.

For 74 years, it guided ships through the shifting channels around the Cape before being deactivated in 1923.

The lighthouse is listed on the National Register of Historic Places and now stands alone in the Wilderness, surrounded by water and sand.

Boat tours pass close enough to see it clearly from the water, framed against the open Atlantic behind it.

Cameras out: seals, terns, dunes and wide coastal skies

Wildlife photographers make a point of getting to Monomoy, and the reasons stack up fast. The seals haul out in concentrated groups, close enough from the tour boats to fill a frame.

Nesting terns and plovers work the beach in numbers rarely seen elsewhere on the coast. The landscape itself, all windswept dune and open marsh, gives you backgrounds that hold up on their own.

The light changes fast out here, the way it does anywhere the land meets open water with no trees to block it.

Real quiet, even in the middle of Cape Cod summer

Chatham is a short drive from some of the busiest beaches on the Cape, but step onto the Morris Island trail or ride out toward South Monomoy and the noise drops away fast.

The Wilderness area draws people who want to walk a beach shared only with seabirds and horseshoe crabs. On the tidal flats, you might watch clammers working the low water in the old Cape Cod way.

The refuge doesn’t have a gift shop or a food stand. What it has is space, and on a crowded summer coast, that’s worth more than most people expect.

Visit Monomoy National Wildlife Refuge in Chatham, Mass.

You can start your visit at the new refuge visitor center at 791 Main St. in downtown Chatham, which opened in fall 2025 and has displays, maps, and trail guides to help you plan your time.

Trail access to the Morris Island unit is free and year-round at 30 Wikis Way, Chatham. For seal viewing on land, low tide at Chatham Lighthouse and Chatham Fish Pier puts you in range without a boat.

Boat tours to the offshore islands run seasonally from Chatham and are the best way to see the seals and the Monomoy Point Light.

This article was created with AI assistance and human editing.

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