Some Louisiana urban environments have a multicultural, multilingual heritage, being so strongly influenced by a mixture of 18th–century French, Haitian, Spanish, French Canadian, Native American, and African cultures that they are considered to be exceptional in the U.S. Before the American purchase of the territory in 1803, the present–day U.S. state of Louisiana had been both a French colony and for a brief period a Spanish one. In addition, colonists imported numerous African people as slaves in the 18th century. Many came from peoples of the same region of West Africa, thus concentrating their culture. In the post–Civil War environment, Anglo Americans increased the pressure for Anglicization, and in 1921, English was for a time made the sole language of instruction in Louisiana schools before a policy of multilingualism was revived in 1974. There has never been an official language in Louisiana, and the state constitution enumerates "the right of the people to preserve, foster, and promote their respective historic, linguistic, and cultural origins".