Things to Do in The Thousand Islands
Island castles and old wooden boats on the St. Lawrence River.
See top-rated activities »About the Thousand Islands
Where Lake Ontario drains into the St. Lawrence River, the river spreads out and breaks into more than 1,800 islands along the border with Canada. Some are large enough for state parks and summer colonies; others hold a single cottage and a boathouse. In the late 1800s, wealthy families from New York and other cities built summer homes here, and the region became one of the country's first great boating playgrounds. Thousand Island salad dressing takes its name from the area, and local tradition places its origin in Clayton.
The most famous sight is Boldt Castle, on Heart Island off Alexandria Bay. George Boldt, manager of the Waldorf-Astoria hotel in New York, began building a six-story stone castle for his wife around 1900, then stopped work when she died suddenly in 1904. The unfinished castle sat empty for decades until the Thousand Islands Bridge Authority bought it in 1977 and began restoring it. Today you can tour the castle, its gardens and the yacht house on a nearby island, reached by shuttle boats and tour boats from Alexandria Bay. Singer Castle, on Dark Island, was built by the president of the Singer sewing machine company and is open for tours in season.
Clayton, a few miles upriver, is the region's other main town. Its Antique Boat Museum has one of the largest collections of freshwater boats in North America, including speedboats, canoes and a houseboat, and offers rides on vintage launches in summer. Tour boats from Clayton and Alexandria Bay cruise past island homes, lighthouses and the international border, and some routes stop at Boldt Castle.
Wellesley Island State Park, reached by the Thousand Islands Bridge, has camping, a nature center and hiking. A passport lets you cross to the Canadian side for Gananoque and Kingston. Most attractions here are seasonal, open roughly mid-May to mid-October, and summer weekends book up early.
Don’t Miss
A restored Gilded Age castle and gardens on an island, open mid-May to mid-October.
A stone castle with secret passages, toured by boat in season.
Historic wooden boats, a restored houseboat and summer launch rides on the river.
Camping, a nature center and trails on one of the largest American islands in the river.
Top-Rated Tours, Tickets & Activities in the Thousand Islands
Viator
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Viator
ViatorTours, tickets, prices and reviews from Viator (a Tripadvisor company) and Tiqets — prices are per person, from, and were checked October 27, 2026. Best in Upstate NY may earn a commission when you book, at no extra cost to you.
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Get free trip quotes »the Thousand Islands — FAQ
Do I need a passport for Boldt Castle?
No, if you go from Alexandria Bay on a U.S. boat that does not stop in Canada. Some tours cross into Canadian waters and stop there; for those, and for Singer Castle tours from Canada, bring a passport.
When is the Thousand Islands season?
Roughly mid-May to mid-October. July and August are busiest; September is quieter and still warm.
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