What Is 1000 island

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Last updated: April 11, 2026

Quick Answer: The Thousand Islands is an archipelago of 1,864 islands spanning the Canada-US border along the Saint Lawrence River, stretching approximately 50 miles downstream from Kingston, Ontario. The islands range from landmasses over 40 square miles to small rocky outcrops, designated as a UNESCO World Biosphere Reserve since 2002. To officially count as one of the Thousand Islands, land must have at least one square foot above water year-round and support two living trees.

Key Facts

The Thousand Islands comprise 1,864 distinct islands along the Saint Lawrence River between Ontario and New York
UNESCO designated the region as a World Biosphere Reserve in 2002, recognizing its ecological significance
The archipelago stretches approximately 50 miles (80 km) downstream from Kingston, Ontario
Islands must meet specific criteria: at least one square foot of exposed land year-round and support minimum two living trees
Kingston, Ontario is the largest population center in the region with over 170,000 in its metropolitan area

Overview

The Thousand Islands is a remarkable archipelago consisting of 1,864 islands situated along the Saint Lawrence River as it emerges from Lake Ontario. This geographic wonder straddles the international border between Canada and the United States, with islands divided between Ontario and New York State. The region extends approximately 50 miles downstream from Kingston, Ontario, creating one of North America's most distinctive and pristine natural regions.

The islands range dramatically in size and character, from substantial landmasses exceeding 40 square miles to small rocky outcroppings barely visible above the water's surface. Some islands support thriving communities and historic castles, while others remain largely uninhabited and serve primarily as wildlife refuges. The Canadian Shield geology that forms these islands creates a unique landscape where ancient rock formations meet the flowing waters of the Saint Lawrence, resulting in exceptional natural beauty and ecological diversity.

How It Works

Understanding what qualifies as one of the Thousand Islands requires specific criteria established to maintain consistency across the archipelago:

Land Requirements: To officially count as one of the Thousand Islands, a piece of emergent land must have at least one square foot (0.093 square meters) of land area above water level year-round, ensuring islands persist through all seasonal water level changes.
Vegetation Standards: Each island must support a minimum of two living trees to be designated as an official Thousand Island, distinguishing them from barren rock outcrops and reinforcing the natural ecosystem requirements.
Political Boundary Division: The international border divides the islands between Canadian territory (Ontario, specifically Frontenac County and the United Counties of Grenville and Leeds) and American territory (New York State, including St. Lawrence and Jefferson Counties).
Geological Formation: The islands represent a southern extension of the Thousand Islands–Frontenac Arch, a branch of the Canadian Shield that connects to the Adirondack Mountains, creating a continuous geological feature spanning the international border.

Key Comparisons

The Thousand Islands region shares characteristics with other famous archipelagos worldwide, though it maintains unique features:

Feature	Thousand Islands	Other Archipelagos
Island Count	1,864 officially designated islands	Greek Islands: 6,000+; Indonesia: 17,000+
Geographic Span	50 miles (80 km) along Saint Lawrence River	Hawaii: 137 miles across; Philippines: 1,150+ miles
International Status	Shared between two nations with defined border	Most archipelagos exist within single nations
Conservation Status	UNESCO World Biosphere Reserve (2002)	Few archipelagos hold this prestigious designation

Why It Matters

Ecological Significance: The 2002 UNESCO World Biosphere Reserve designation recognizes the region's exceptional biodiversity, including habitat for migratory birds, fish populations, and unique vegetation adapted to the shield landscape.
Tourism and Recreation: The Thousand Islands attracts hundreds of thousands of visitors annually for boating, fishing, sightseeing, and historical tourism, supporting the regional economy across both Canadian and American communities.
Historical Importance: The region served as a vital transportation corridor and military frontier throughout North American history, with numerous historic sites, lighthouses, and Victorian-era mansions still visible today.
International Cooperation: The shared archipelago requires ongoing cooperation between Canadian and American governments for environmental protection, navigation safety, and economic development along the border.

The Thousand Islands represents far more than simply a collection of rocky outcrops in a river. This UNESCO-designated biosphere reserve embodies the intersection of geology, history, ecology, and international relations, making it a globally significant natural and cultural landscape. Its designation as a World Biosphere Reserve underscores the importance of preserving this unique ecosystem for future generations while balancing tourism, conservation, and the sustainable use of natural resources across an international boundary.