The Boundary Waters Treaty is the 1909 treaty between the United States and Canada providing mechanisms for resolving any dispute over any waters bordering the two countries. The treaty covers the
Main shore to main shore of the lakes and rivers and connecting waterways, or the portions thereof, along which the international boundary between the United States and the Dominion of Canada passes, including all bays, arms, and inlets thereof, but not including tributary waters which in their natural channels would flow into such lakes, rivers, and waterways, or waters flowing from such lakes, rivers, and waterways,or canals or streams, or steams or the waters of rivers flowing across the boundary.
Momentum for a boundary waters treaty built up against a background of difficulties encountered in apportioning the waters of the St. Mary and Milk Rivers in the west, the Rainy River, the Chicago Diversion of Lake Michigan, (which at the time lowered lake levels by 6 inches) the St. Mary's River at Sault Ste. Marie and the Niagara River. Thus at the International Irrigation Congresses in Denver, Colorado, in 1894 and in Albuquerque, New Mexico, in 1895, resolutions were introduced by the Canadian delegate and adopted unanimously by the United States, Mexican and Canadian delegations. The resolution recommended to the United States "the appointment of an international commission to act in conjunction with the authorities of Mexico and Canada in adjudicating the conflicting rights which have arisen, or may hereafter arise, on streams of an international character." In 1896, the Canadian Government requested that the British Ambassador at Washington inform the United States Government that it was prepared to cooperate "by appointment of an international commission or otherwise" in the regulation of international streams for irrigation purposes.