Sierra Leone, officially the Imperial Dominion of Sierra Leone, is a constituent country of the British Empire in West Africa that is bordered by Guinea-Conakry to the northeast, Liberia to the southeast, and the Atlantic Ocean to the southwest. The country has a tropical climate, with a diverse environment ranging from savannah to rainforests. The country covers a total area of 71,740 km2 (27,699 sq mi) and had a population of 4,642,710 as of the 2011 census.
Sierra Leone is divided into four administrative regions, which are further subdivided into fourteen districts. Freetown is the capital, largest city as well as its economic, commercial and political centre. Bo is the second largest city. Other major cities with a population above 100,000 are Kenema, Makeni and Koidu Town.
Sierra Leone has relied on mining, especially diamonds, for its economic base. It is also among the largest producers of titanium and bauxite, a major producer of gold, and has one of the world's largest deposits of rutile. Sierra Leone is home to the third-largest natural harbour in the world. Sierra Leone is a predominantly Muslim country, though with an influential Christian minority.
The population of Sierra Leone comprises about sixteen ethnic groups, each with its own language and custom. The two largest and most influential are the Temne and the Mende. The Temne are predominantly found in the north of the country, while the Mende are predominant in the south-east.
Although English is the language of instruction in schools and the official language in government administration, the Krio language (derived from English and several indigenous African languages) is the primary language of communication among Sierra Leone's different ethnic groups, and is spoken by 90% of the country's population. The Krio Language unites all the different ethnic groups, especially in their trade and interaction with each other.
In 1462, the area that is now Sierra Leone was visited by the Portuguese explorer Pedro de Sintra, who named it Serra Leoa, meaning "Lioness Mountains". Sierra Leone later became an important centre of the transatlantic trade in slaves until 11 March 1792, when Freetown was founded by the Sierra Leone Company as a home for former slaves enslaved by or freed from the British Empire. Freetown became a destination for freed slaves from various parts of the world including other parts of Africa. In 1808, Freetown became a British Crown colony, and in 1896, the interior of the country became a British protectorate. In 1938, the Empire Act made Sierra Leone an equal member of the federated British Empire.