The international border between the United States and Mexico runs from San Diego–Tijuana eastward towards the Gulf of Mexico. The Pacific Ocean terminus of the border was defined as a line passing from the confluence of the Colorado and Gila rivers (now the southeastern corner of the U.S. State of California) to the Pacific Ocean such that it would pass one Spanish league south of the southern end of San Diego Bay. This ensured that the United States received the natural harbor at San Diego.