The Continental Divide of the Americas is the principal, and largely mountainous, hydrological divide of the Americas. This divide runs from Cape Prince of Wales in western Alaska, through the Rocky Mountains of western Canada and the continental United States, then through the Sierra Madre Occidental mountains in Mexico, through Central America and along the Andes Mountains of South America. Continental divides separate one drainage basin from another. They are used to define the direction that an area's rivers flow and drain into the oceans and seas. The best-known continental divide is in North America and it runs along the Rocky and Andes mountain ranges