Waterton Lake is a mountain lake in southern Alberta, Canada and northern Montana, United States. The lake is composed of two bodies of water, connected by a shallow channel known locally as the Bosporus. The two parts are referred to as Middle Waterton Lake, and Upper Waterton Lake, the latter of which is divided by the Canada–United States border with Canada containing about two thirds of the lake while the Southern third falls in the United States. The United States Geological Survey gives the geocoordinates of 49°03′00″N 113°54′03″W for Upper Waterton Lake. There is also Lower Waterton Lake which is located to the north of Middle Waterton Lake; it is separated by a channel known as the Dardanelles.