Uninhabited until 1456, the 10 volcanic islands of Cabo Verde prospered during the 16-17th centuries attracting merchants, pirates and privateers. Privateers were private ships or people, permitted by governments to engage in acts of maritime war. The Atlantic Slave Trade was the engine of growth for the area, and it went into economic decline after the 19th century end of slavery. After being an overseas department of Portugal, independence came in 1975. As a trading post, there has been centuries of mixing and 71% of the population of half a million people are descendants of both Africa and Europe. While the official language is Portuguese, the Creole language is a mixture of Portuguese and West African words. The International Airport is named after Nelson Mandela.