8 March 1957
Ghana was admitted to the United Nations on 8 March 1957, two days after it achieved independence from Britain. The country which had previously been known as the Gold Coast had been under British rule since 1821. In 1954, Kwame Nkrumah became Prime Minister and led the way to independence. After gaining independence, Ghana went through several territorial reorganisations. Nkrumah was later overthrown. Today, Ghana is a democratic state.
References

About African History, A Brief History of Ghana, from About.com, [online], Available at africanhistory.about.com [Accessed: 26 February 2014]|Ghana Web, History of Ghana, from Ghana★Web, [online], Available at www.ghanaweb.com [Accessed: 26 February 2014]