Since its founding in 1625 by Dutch traders as New Amsterdam, New York City has been a major destination for immigrants of many nationalities who have formed ethnic enclaves, neighborhoods dominated by one ethnicity. Freed African American slaves also moved to New York City in the Great Migration and the later Second Great Migration and formed ethnic enclaves. These neighborhoods are set apart from the main city by differences such as food, goods for sale, or even language. Ethnic enclaves provide inhabitants security in work and social opportunities, but limit economic opportunities, do not encourage the development of English speaking, and keep immigrants in their own culture.