Mexico is situated in North America, although culturally, it is identified more closely with Central and South American countries. It borders the United States in the north, Guatemala and Belize in the south, the Pacific Ocean in the west, and the Gulf of Mexico in the east. The national territory measures more than 750,000 square miles (nearly two million square kilometers) and contains a wide range of physical environments and natural resources. Two huge mountain chains—the Western Sierra Madre and the Eastern Sierra Madre—run from north to south and meet in central Mexico. East and west of the mountain chains are strips of humid coastal plains. The entirely flat Yucatán peninsula in the southeast is an exception in mountainous Mexico. The possibilities and limitations of this topographic and climatic system have had a strong influence on Mexico's social, economic, and cultural organization.