A continental divide is an imaginary line down a continent that demarcates whether water in the area will flow towards a given body of water (usually an ocean) or another. The most famous continental divide is the north-south Continental Divide of the Americas, sometimes known as the Great Divide or just the Continental Divide. This divide is more than 6,000 miles (9,600 km) long, stretching from the western tip of Alaska all the way to Tierra del Fuego at the southernmost tip of South America. This continental divide mostly demarcates whether water flows into the Pacific or Atlantic Ocean. Some areas close to the divide, like the Great Basin, are endorheic basins, meaning that they retain water in salt lakes or salt pans, and it never flows to the ocean.
In the United States, the Continental Divide does not go clear down the middle of the country, but follows the peaks of the Rocky Mountains, which are somewhat offset to the west. Immediately east of the Rocky Mountains and throughout most of the central United States, water flows to the Gulf of Mexico. In eastern North America there are three more continental divides: the Northern Divide, Eastern Divide, and the St. Lawrence Seaway Divide. These divides indicate whether water flows to the eastern seaboard, Hudson Bay and the Arctic Ocean, or the Gulf of St. Lawrence. For much of its length, the Northern Divide is located roughly at the border between the United States and Canada.
At Triple Divide Peak in Glacier National Park, in Montana, two important continental divides converge -- the Great Divide and the Northern Divide. There is a triple junction between the two branches of the Great Divide and the one branch of the Northern Divide, which begins at this point and runs east. Depending on where precisely on the peak you are standing, a drop of water will eventually flow to either the Gulf of Mexico, the Pacific Ocean, or the Arctic Ocean. Scientists consider this the hydrological peak of North America.
Continental divides worldwide dictate numerous features of the continents around them. Glaciers slowly flow in directions away from continental divides, carving out huge valleys and fjords in their wake. River systems flow away from continental divides, and many lakes which occupy glacier-carved valleys point away from continental divides. Oftentimes, a continental divide can be clearly seen just by looking at a high-resolution satellite photo of an area.