In the early 19th century Basuto Chief Moshoeshoe united tribes in this mountainous land surrounded by South Africa. To establish a buffer against Boer expansion, he asked the British to administer the kingdom. Lesotho became independent in 1966. In 1993 it became a constitutional monarchy. Water is Lesotho's major natural resource. Completion of a large hydropower plant in 1998 helps the economy expand through the sale of water to South Africa.