continental divide

An imaginary line across a continental mass, forming the boundary between watersheds and determined by the division between rivers flowing in opposite directions. In western North America, the Continental Divide follows the crest of the Rocky Mountains for most of its length.

On the east of the North American Continental Divide, all rivers flow ultimately into the Atlantic Ocean, either (as part of the Mississippi River system) directly into the Gulf of Mexico, or (in the north) by way of Hudson Bay. In the north, where the Divide swings west, some flow into the Arctic Ocean. On the west of the Divide, all rivers flow to the Pacific Ocean and its arms (for example, the Gulf of California in Mexico). In the USA, the Divide (from the south) winds through several ranges in southwest New Mexico, and passes west of Albuquerque; in Colorado, it swings west through the San Juan Mountains, then northeast to the Sawatch Range and northeast and north-northeast to Rocky Mountain National Park, west to near Steamboat Springs, and north-northwest into Wyoming. In southwestern Wyoming, it passes around both sides of the Great Divide Basin and runs northwest along the Wind River Range to Yellowstone National Park. It defines the Montana-Idaho border in the Beaverhead and Bitterroot ranges, then swings east around Butte and north and north-northwest to Glacier National Park. In Canada, it forms much of the Alberta-British Columbia border, crosses north British Columbia into the Yukon Territory, forms part of the Yukon Territory-Northwest Territories border (the Logan Mountains), and finally swings west across the Yukon to Alaska, following the crest of the Brooks Range west-southwest, to the western tip of the Seward Peninsula.