The Slave Coast is the name of the coastal areas of present Togo, Benin (formerly Dahomey) and western Nigeria, a fertile region of coastal Western Africa along the Bight of Benin. In pre-colonial times it was one of the most densely populated parts of the African continent. It became one of the most important export centers for the Atlantic slave trade from the early 16th century to the 19th century.
Other West African regions historically known by their prime colonial export are Gold Coast (modern-day Ghana), Ivory Coast (modern-day Côte d'Ivoire), and Pepper Coast (or Grain Coast, in modern-day Liberia).
According to most research, the beginnings of the slave trade in this area are not well documented. It is difficult to track the development of trade in this area and its integration into the Atlantic slave trades before about 1670, when European sources begin to document this interaction.
The slave trade became so extensive in the 18th and 19th centuries that an “Atlantic community” was formed. The slave trade was facilitated on the European end by the Portuguese (mostly by Portuguese Empire's Brazilians), the Dutch, the French and the British. Slaves went to the New World, mostly to Brazil and the Caribbean. Ports that exported these slaves from Africa include Ouidah, Lagos, Aného (Little Popo), Grand-Popo, Agoué, Jakin, Porto-Novo, and Badagry. These ports traded in slaves that were supplied by African communities, tribes and kingdoms, including the Alladah and Ouidah, which were later taken over by the Dahomey kingdom.
Researchers estimate that between 2 and 3 million slaves were exported out of this region and were traded for goods like alcohol and tobacco from the Americas and textiles from Europe. This complex exchange fostered political and cultural as well as commercial connections between these three regions. Religions, architectural styles, languages, knowledge, and other new goods were mingled at this time. Slaves as well as free men used the exchange routes to travel to new places which aided in hybridizing European and African cultures. Intermarriage has been documented in ports like Ouidah where Europeans were permanently stationed. Communication was quite extensive between all three areas of trade, to the point where even individual slaves could be tracked. 
After slavery had been abolished by European countries, the slave trade continued for a time with independent traders (instead of government agents). Cultural integration had become so extensive that the defining characteristics of each culture were increasingly broadened. In the case of Brazilian culture—which had differentiated itself from Portuguese culture through its combination of African, Portuguese and New World traditions—Brazilian-style dress, cuisine and speaking Portuguese had become the main requirements for Brazilian identity, regardless of ethnicity, religion, or geographic location. 
References and sources
- Law, p.307
- Law, p.319
- Law, p.327
- Law, Robin. The Slave Coast of West Africa 1550-1750: The Impact of the Atlantic Slave Trade on an African Society. Clarendon Press, Oxford, 1991.
- Law, Robin and Kristin Mann. “African and American Atlantic Worlds.” The William and Mary Quarterly, 3rd Ser., 56:2 Apr. 1999, pp. 307–334.
- Shillington, Kevin. History of Africa. 2nd Edition, MacMillan Publishers Limited, NY USA, 2005.
- St Clair, William. The Door of No Return: The History of Cape Coast Castle and the Atlantic Slave Trade. BlueBridge.