The Thousand Islands is the name of an archipelago of islands that straddle the U.S.-Canada border in the Saint Lawrence River as it emerges from the northeast corner of Lake Ontario. They stretch for about downstream from Kingston, Ontario. The Canadian islands are in the province of Ontario. The U.S. islands are in the state of New York. The islands, which number 1,793 in all, range in size from over to smaller islands occupied by a single residence, to even smaller uninhabited outcroppings of rocks that are home to migratory waterfowl. The number of islands was determined using the criteria that any island must be above water level for 365 (366) days per year, bigger than one square foot (roughly 930 cm²), and support at least one living tree. The area is very popular among vacationers, campers, and boaters, and is often referred to as the "fresh water boating capital of the world".
The area is frequently traveled by large freighters traveling the St. Lawrence Seaway, but is so riddled with shoals and rocks that local navigators are hired to help the vessels travel through the hazardous waterway. Under the Canadian span, a vessel just less than 25 feet (7.6 m) offshore can find itself in over 200 feet (61 m) of water. Similarly, rocks and shoals less than two feet (61 cm) underwater can be found in the center of channels 90 feet (27 m) deep. Because of the great number of rocks and shoals just above or below the water's surface, it is unwise to travel the waters at night, unless one stays in the main channels and has charts, a chart plotter, or knows the area well. The water is so clear in some areas, that a rocky bottom can be observed in 80 feet (24 m) of water. The area features several shipwrecks and is a great place for diving. Although most of the wrecks are over 100 feet (30 m) underwater, some are a mere 15 feet below the water's surface and can be seen by looking overboard.
Around twenty of these islands form the St. Lawrence Islands National Park, the smallest of Canada's national parks. The Thousand Islands-Frontenac Arch region was designated a World Biosphere Reserve by UNESCO in 2002. The U.S. islands include numerous New York state parks, including Robert Moses State Park - Thousand Islands, located on an island in the St. Lawrence.
In the late nineteenth century and early twentieth century many distinguished visitors made the region widely known as a summer resort. Several grand hotels provided luxurious accommodations while steamboats offered extensive tours among the islands. Wealthy and middle-class summer residents built summer homes. Some masonry "castles" remain as international landmarks. The most famous extant examples are "The Towers" on Dark Island, now called Singer Castle, and the long-neglected Boldt Castle on Heart Island, which is slowly being restored.
During the half century (1874-1912) of the resort's greatest prominence, most wealthy vacationers came from New York City, joined by prominent families from Chicago, Pittsburgh and other cities of the United States and Canada. The region retains a historically important collection of vacation homes from this time. The Thousand Islands have long been a center for recreational boating. Large steam yachts, many designed by Nathanael Herreshoff required distinctive yacht houses. The region was known also for innovative power boating during this period. Three local yacht clubs hosted the Gold Cup Races of the American Power Boat Association for nine consecutive years. The Antique Boat Museum of Clayton, New York retains one of the world's major collections of recreational freshwater boats.
The Thousand Islands Bridge connects New York State and Ontario by traversing Wellesley Island at the northernmost point of U.S. Interstate 81 in Jefferson County and meets Highway 137, which leads to Highway 401. The Thousand Islands Parkway provides a scenic view of many of the islands.
The largest island in the group, Wolfe Island, is located entirely in Ontario. Adjacent to Wolfe but closer to New York is Carleton Island, the site of a ruined fort, Fort Haldiman, built in 1779 by the British during the American Revolutionary War. The island was captured by three American soldiers during the War of 1812 and remains part of the United States today.
The Thousand Islands gave their name to the popular Thousand Island Dressing around the turn of the twentieth century when Sophie LaLonde, of Clayton, New York who served the dressing at dinner for guests of her husband, a popular fishing guide, gave the recipe to Clayton hotel owner Ella Bertrand and New York City stage actress May Irwin. Irwin shared it with hotel magnate George C. Boldt.
The towns most associated with the Thousand Islands are Alexandria Bay, New York, and Gananoque, Ontario. On both sides, free dock space is available to boaters who wish to come ashore and walk through the towns, with souvenir shops, restaurants, ice cream parlors, pizza shops and arcades located nearby.
Another popular American vacation spot is the Wellesley Island State Park on Wellesley Island, which sports hundreds of camping sites, both powered and non, and several boat ramps and docking facilities for a boater-friendly park.