27 April 1961
West African state Sierra Leone fronts onto the Atlantic Ocean, and is flanked by Liberia and Guinea.
The very earliest inhabitants of Sierra Leone were possibly the Bulom people. The 15th century saw the Mende, Temne and Fulani peoples follow them. The first European explorers were the Portuguese.
References
BBC, 1961: Sierra Leone wins independence, from BBC NEWS, [online], Available at news.bbc.co.uk [Accessed: 29 April 2014]|Fyfe, C., Independence, from Encyclopædia Britannica, [online], Available at www.britannica.com [Accessed: 29 April 2014]