The point of origin of a stream is often called the headwaters or source. The entire basin drained by the stream is termed the watershed. Every watershed is made up of smaller watersheds, while most watersheds are parts of larger watersheds. For instance, the Continental Divide in North America divides the Atlantic Ocean watershed from the Pacific Ocean watershed, but the Atlantic Ocean watershed may be first divided into the Atlantic Ocean drainage and the Gulf of Mexico drainage. This delineation within the United States is termed the Eastern Divide. The Gulf of Mexico watershed may be divided into Mississippi River basin and a number of smaller watersheds, such as the Tombigbee River watershed.