Arkansas is one of the Southern states of the USA. With a population of approximately 3 million, Arkansas is located on an area of 137,754 km². It is divided into two geographical areas: Highlands and plains. The plains to the east and west consist of the Mississippi Alluvial and the West Gulf Coastal plain. The mountainous regions to the north and west are the Ozark Plateau, the Ouachita Mountains and the Arkansas river valley flowing through them.