[2][3] The Thousand Islands archipelago is at the outlet of Lake Ontario at the head of the Saint Lawrence River.

As is usual in inland waters of the United States and Canada, vessels must use maritime pilots to help them travel safely.

Due to the great number of rocks and shoals just above or below the water's surface, navigation outside of the marked channels at night can be dangerous.

The city marks the western end of the region in Canada, while Brockville, Ontario, to the east, is the other large population center.

The American region along the river is much less dense; the largest city is Watertown, New York, which has a population of 25,000 (2020) and is twenty miles (32 km) inland.

In New York, United States[7] This region is within Jefferson County: In Ontario, Canada[7] This region includes the southern areas of Frontenac and Leeds & Grenville counties: O boating on the rivers, The voyage down the St. Lawrence, the superb scenery, the steamers, The ships sailing, the Thousand Islands, the occasional timber-raft and the raftsmen with long-reaching sweep-oars, The little huts on the rafts, and the stream of smoke when they cook supper at evening.

Prior to European colonization, the Thousand Islands region was home to, or visited by, members of the Iroquois Confederacy and Ojibwa people.

Three local yacht clubs hosted the Gold Cup Races of the American Power Boat Association for nine consecutive years.[when?]

The park hosts campgrounds, inland walking trails, annual family events, as well as a national heritage building.

Many of these river parks were established in the late 19th and early 20th century as part of the St. Lawrence Reservation,[24] and were among New York's earliest land acquisitions for the purpose of preservation and recreational development.

Maxson Airfield (FAA LID: 89NY) is a privately owned, private-use general aviation airport two nautical miles (3.7 km; 2.3 mi) south of the central business district of Alexandria Bay, a village in Jefferson County, New York.

Brockville-Thousand Islands Regional Tackaberry Airport (IATA: XBR, TC LID: CNL3), also known as Brockville Municipal Airport, is a registered aerodrome in Elizabethtown-Kitley Township, 4.8 nautical miles (8.9 km; 5.5 mi) northwest of the city of Brockville, Ontario, Canada.

[31] One common story describes how a fishing guide's wife, Sophia LaLonde, made the condiment as part of her husband George's shore dinner.