The Thousand Islands is the name of an archipelago of islands that straddle the Canada-USA border in the Saint Lawrence River as it emerges from the northeast corner of Lake Ontario. They stretch for about 80 km 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 40 square miles (100 km²) to smaller islands occupied by a single residence, to even smaller uninhabited outcroppings of rocks that are home to migratory waterfowl.

 On the postcard we can see Boldt Castle which is located on Heart Island (New York).