The St. Lawrence River hides castles, shipwrecks, and a world-record island in upstate New York

There’s more here than you’d expect

The St. Lawrence River along New York’s northern border holds 1,864 islands, a UNESCO biosphere, two Gilded Age castles, and what many consider the world’s smallest inhabited island.

Some of these islands are large enough for state parks and golf courses. Others barely fit in a tree.

Alexandria Bay sits on the American side and works as your base for all of it. The river looks wide and calm from the shore.

Once you get out on it, you start to understand the scale.

These islands are ancient mountaintops

About 10,000 years ago, glaciers retreated across this part of North America and the St. Lawrence flooded a landscape of worn-down mountains.

What you see poking above the water today are the tops of those mountains.

The archipelago stretches about 50 miles downstream from Lake Ontario, straddling the U.S.-Canada border. Some islands are large enough to hold homes, campgrounds and nature centers.

Others are just a slab of granite with a single tree growing out of a crack in the rock.

Millionaires discovered this river in the 1800s

Long before any castle went up, people had lived along this river for thousands of years.

By the late 1800s, wealthy Americans from New York and beyond started arriving each summer, building lavish estates along what locals called Millionaire’s Row. Tourism took hold and never let go.

The region has run on it for more than 150 years. And somewhere along the way, someone in one of these river towns started mixing mayonnaise, ketchup and relish together.

The Thousand Islands still claim credit for that dressing, though neighboring villages dispute it.

George Boldt built a castle for the woman he loved

In 1900, George Boldt, the proprietor of New York City’s Waldorf-Astoria Hotel, started construction on a six-story, 120-room Rhineland-style castle on a small island in the river.

He had the island reshaped into the form of a heart and renamed it Heart Island. The castle came with tunnels, Italian gardens, a drawbridge and a powerhouse.

Around 300 workers, including stonemasons, carpenters and artists, worked the site. Boldt built it as a gift for his wife, Louise.

One telegram stopped 300 workers cold

In January 1904, Louise Boldt died suddenly. Boldt sent a telegram to Heart Island ordering every worker to stop immediately.

They did. He never came back to the island, though he continued to summer in the Thousand Islands until his death in 1916. For 73 years, the unfinished castle sat open to the weather and vandals.

Wind came through broken windows. Graffiti covered the walls.

The river slowly worked on it, year after year, while the story behind it passed from one generation to the next.

See how the castle was brought back to life

In 1977, the Thousand Islands Bridge Authority bought Heart Island for one dollar, agreeing to put all castle revenue toward restoration.

By 2020, more than $50 million had gone into the work, with crews returning each season.

You can now walk through a grand staircase, past marble floors, beneath a restored stained glass dome and through the servants’ quarters.

The castle is open mid-May to mid-October, but you can only reach it by boat from Alexandria Bay or other departure points nearby.

The Boldt Yacht House on Wellesley Island is worth a stop, too, with antique wooden boats from the era on display.

Singer Castle hides secret passages on Dark Island

A few miles away on Dark Island stands Singer Castle, built in 1905 for Frederick Gilbert Bourne, president of the Singer Manufacturing Company.

Architect Ernest Flagg drew inspiration from a castle in a Sir Walter Scott novel when he designed the 28-room structure. Pull a specific book off a library shelf and a hidden panel opens.

That’s one of the castle’s secret passageways. There’s also a dungeon and a clock tower.

Guided tours run 45 minutes. If you want to stay the night, you can rent the Royal Suite.

The world’s smallest inhabited island fits in your backyard

Between Heart Island and Imperial Isle, close to the U.S.-Canada border, sits Just Room Enough Island. The name is accurate.

The whole thing covers about 3,300 square feet, roughly one-thirteenth of an acre. The Sizeland family bought it in the 1950s, built a cottage, planted a tree and put out two benches.

That’s everything on it.

You can’t visit because it’s private property, but every boat tour passes close enough that you won’t miss it.

Wellesley Island has camping, hiking and winter fishing

Wellesley Island State Park is the biggest camping complex in the Thousand Islands, with 432 sites. The park has a sandy beach, a nine-hole golf course, a full-service marina with four boat launches and a camp store.

The Minna Anthony Common Nature Center covers a 600-acre peninsula with hiking trails, live animal exhibits and a seasonal butterfly house. Fishing runs strong here, especially for muskie, pike and smallmouth bass.

Winter brings a different crowd for cross-country skiing, snowshoeing and ice fishing.

Walk through a Victorian neighborhood frozen in the 1870s

On the western end of Wellesley Island, a residential community called Thousand Islands Park has stood since the late 1870s.

More than 300 Victorian-era homes have been preserved there, and driving through it feels like the calendar stopped somewhere around 1895. Ornate gingerbread trim lines the eaves.

Wraparound porches face the river. Cottage gardens fill the small yards.

Small shops and diners sit between the houses. Most people drive through once and then loop back around.

Climb an 1848 lighthouse and look down into the river

Rock Island Lighthouse went up in 1848, making it one of the oldest on the St. Lawrence. You can climb its spiral staircase to the lantern room and look out over the river in every direction.

The keeper’s house is now a maritime museum. Like Boldt Castle, the island is only reachable by boat, with tours running out of Clayton.

If the lighthouse isn’t enough river history, glass-bottom boat tours go out over the shipwrecks scattered across the St. Lawrence floor, and you see them without getting in the water.

Clayton’s boat museum holds 300 years of river craft

About 15 minutes from Alexandria Bay, the village of Clayton is home to the Antique Boat Museum, spread across a 4.5-acre waterfront campus. More than 300 antique and classic boats fill the collection.

You can walk through George Boldt’s historic two-story houseboat, take a speedboat ride out among the islands, or row a St. Lawrence skiff yourself.

The museum also runs the longest continuously running annual antique boat show and auction in the country. Clayton’s downtown adds shops, galleries and waterfront dining to the mix.

Five forests meet here and 80 fish species live below

The Thousand Islands sit within the Frontenac Arch, an ancient granite ridge that links the Canadian Shield to the Adirondack Mountains. UNESCO designated this region a World Biosphere Reserve in 2002.

Five separate forest regions converge here, making it one of the most biodiverse areas in northeastern North America. The islands act as a land bridge for migrating birds.

More than 80 fish species live in the St. Lawrence along this stretch. In winter, bald eagles gather near Wellesley Island, drawn by the open water and the fish below it.

Explore the Thousand Islands from Alexandria Bay, New York

Alexandria Bay works as your starting point for almost everything in the region.

The village waterfront is where most boat tours leave from, including narrated cruises, castle shuttles and dinner cruises aboard paddle wheel boats.

Downtown has shops, galleries, mini-golf, go-karts and arcades if you’re traveling with kids. Scenic View Park runs along the riverfront with walking paths and open views of the islands.

The 1000 Islands Tower rises 400 feet above the trees and gives you one of the clearest unobstructed views of the whole archipelago.

Visit Alexandria Bay on New York’s St. Lawrence River

You can find Alexandria Bay at the junction of Route 12 and Church Street in Jefferson County, northern New York.

Most boat tour operators run out of the village waterfront, with tours starting around $30 to $40 for adults, depending on the itinerary. Boldt Castle admission is separate and runs about $12 for adults.

The 1000 Islands Tower charges a few dollars for the elevator ride to the top. Summer is peak season, so arrive early if you’re coming on a weekend in July or August.

Check the official website for current tour schedules and departure times before you go.

This article was created with AI assistance and human editing.

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