Liberia is a republic located on the west coast of Africa. The country is bounded by Guinea in the north, Ivory Coast in the east and Sierra Leone in the north-west, with access to the Atlantic Ocean. Earliest recorded history of the region dates back to the twelfth century with the migration of tribal groups from the north, during the decline of the Mali and later Songhai Empires. The area was explored by the Portuguese, Dutch, and British from the fifteenth century onwards and because of the abundance of melegueta pepper, it became known as the Pepper Coast by traders. In 1822, the American Colonization Society founded a colony for freed slaves near present-day Monrovia, and other philanthropic societies assisted in the passage of freed slaves to colonies designated Mississippi-in-Africa and the Republic of Maryland. These colonies would be annexed as part of a united Liberia which declared independence in 1847, with Joseph Jenkins Roberts as first president. The history of Liberia would be influenced by the uneasy political relationship between the descendants of the colonists (Americo-Liberians) and ethnic groups such as the Krahn and Mandinka peoples. In 1980, President William R. Tolbert was assassinated in a coup led by Samuel Doe, and in successive years the country has experienced numerous coup attempts and two civil wars. The capital and major port is Monrovia. Estimated population of Liberia in 2011 was 4,128,572.