Sierra Leone gained its independence in 1961.
To put it simply, gaining independence means that a country is no longer controlled by another country. In the case of Sierra Leone, it was a British colony, which means that the British government was in charge of the country. However, after years of struggle and resistance by Sierra Leonean activists and politicians, Sierra Leone became an independent country in 1961. This means that the people of Sierra Leone were finally able to govern themselves and make their own decisions about how their country should be run.