Southern Alberta is in the northern Great Plains region, lined to the east from the Canadian Rocky Mountains and their foothills. The rest of the region is dominated by the semi-arid prairies of the Palliser's Triangle, where farms and ranches have been built, often with the help of irrigation. Rivers generally flow from west to east and include the Oldman River, Bow River, Red Deer River, South Saskatchewan River, and Milk River. Milk River is the only river in Canada that eventually flows into the Gulf of Mexico.