Primary Publications

This list of publications relate to published academic research underpinning the presentation of annual maps hosted on this website: 

Ashton Wiens, Henry B. Lovejoy, Zachary Mullen, Eric Vance, "Estimating Conditional Probabilities of Historical Migrations in the African Diaspora Using Kriging and Markov Decision Process Models," Journal of the Royal Statistical Society Series A "Statistics in Society," currently under review and submitted Aug. 2020. For pre-publication see

Henry B. Lovejoy, "Mapping Uncertainty: The Collapse of Oyo and the trans-Atlantic Slave Trade, 1816-1836," Journal of Global Slavery 4, 2 (2019): 127-161. (Open source access).

Henry B. Lovejoy, "Re-Drawing Historical Maps of the Bight of Benin Hinterland, c. 1780," Canadian Journal of African Studies 47, 3 (2013): 443-463.

Research Materials

This select bibliography contains information about the datasets, primary and secondary sources from which the mapping data derives:


DIVA-GIS. (Accessed 2014).

Eltis, David. dir. (Accessed 2019). Voyages: The Trans-Atlantic Slave Trade Database.

Eltis, David, and Misevich, Philip, dirs. (accessed in 2019). African Origins.

Lovejoy, Henry B., dir. (accessed 2020). Liberated Africans.

Natural Earth. (Accessed 2014).

Primary Sources

The key primary sources from which these data derive require further explanation due to historical uncertainties. In some cases, transient European explorers witnessed warfare at places without fully understanding the local or regional context. Otherwise, missionaries recorded the experiences of enslavement for Africans several years after they boarded slave ships and were liberated in British abolition efforts in Sierra Leone. This small selection of written contemporary sources can of course be supplemented with oral traditions, but verbal recollections are often difficult to date with any precision, or to cross-reference with the documentation. Shipping data appear to be much more reliable, but it too contains gaps oftentimes surrounding the arrival and departure dates, and at other times, ports of embarkation were unspecified in the documentation. As the scholarship cited herein has long proven, many people were transported to the Americas from places in and around Oyo during the period of intense conflict after 1816, but from where and when exactly, and in what numbers, remains more obscure, especially in consideration of the internal slave trade. Moreover, not all people leaving the Bight of Benin were enslaved through warfare in this period, but via historical trade routes and networks.

Primary sources used in this study derive from the observations of foreign diplomats and former slaves educated by Protestant missionaries. Hugh Clapperton, a British diplomat, traveled from Badagry through the Oyo capital in 1825–1826 and onto Sokoto where he died in 1827. Clapperton’s journal survived because his servant, Richard Lander who also wrote about his experiences, returned back south through Oyo to Badagry after Clapperton’s death. In 1830, Richard Lander, along with his brother John, traveled inland again from Badagry to Bussa in Borgu and then down the Niger in order to map the course of the river to the delta. Otherwise, the narratives of Samuel Ajayi Crowther of Oyo, Joseph Wright of the Egba and Osifekunde of Ijebu provide firsthand accounts of enslavement in the 1820s, including references to the destruction of many towns and shifting trade routes in high conflict zones. Another key source is Samuel Johnson, whose parents were from Oyo and were taken to Freetown in British campaigns to blockade the slave trade. Born in Sierra Leone, Johnson was educated by the Church Missionary Society, and as a missionary, he returned to the Bight of Benin hinterland where he subsequently recorded Oyo oral traditions. By 1897, he had completed a work documenting the history of the Yoruba states, including accounts related to the destruction of towns. Other missionaries, such as Edward Irving, recorded more information in Ijebu territory in the 1850s, especially in relation to the destruction of many Egba towns. A French abbot, Thomas Mouléro, provided a list of annual campaigns of King Gezo of Dahomey between 1818 and 1857. And finally, Voyages and Liberated Africans data allow projections on the numbers of people boarding slave ships, especially at ports between Little Popo and Lagos.

Ajayi, J. F. Ade. (1967). Samuel Ajayi Crowther of Oyo.” In: P. Curtin, ed., Africa Remembered: Narratives by West Africans from the Era of the Slave Trade. Madison: University of Wisconsin Press, pp. 289-316.

Bruce Lockhart, Jamie, and Lovejoy, Paul E., eds. ([1829] 2005). Hugh Clapperton Into the Interior of Africa: Records of the Second Expedition, 1825-1827. Leiden: Koninklijke Brill N.V.

Curtin, Philip. ([1839] 1967). "Joseph Wright of the Egba." In: Philip Curtin, ed., Africa Remembered: Narratives by West Africans from the Era of the Slave Trade, 318-320. Madison: University of Wisconsin Press. 

Hazoumé, Paul. ([1938] 1978). Doguicimi. Paris: Maisonneuve et Larose.

Irving, Edward. (1856). Ijebu Country. Church Missionary Intelligencer 7, pp. 65-72, 93-8 and 118-20.

Johnson, Samuel. (1921). The History of the Yorùbás from the Earliest Times to the Beginning of the British Protectorate. London: Routledge & Sons Limited.

Lander, Richard. (1830). Records of Captain Clapperton’s Last Expedition to Africa. 2 vols. London: Colburn and Bentley.

Lander, Richard, and Lander, John. (1832). Journal of an Expedition to Explore the Course and Termination of the Niger. 2 vols. London: John Murray.

Le Herissé, A. (1911). L’ancien royaume de Dahomey. Paris: E. Larose.

Lloyd, Peter C. ([1841] 1967). Osifekunde of Ijebu. In: P. Curtin, ed., Africa Remembered: Narratives by West Africans from the Era of the Slave Trade. Madison: University of Wisconsin Press, pp. 217-88.


Select Secondary Sources

Ajisafe, Ajayi Kolawole. (1964). The History of Abeokuta. Abeokuta: Fola Bookshops.

Anignikin, Sylvain C. (2001). “Histoire des populations mahi: À propos de la controverse sur l'ethnonyme et le toponyme ‘Mahi,’” Cahiers d'Études Africaines 41 (162), 243-65.

Apter, Andrew. (2013). "Yoruba Ethnogenesis from Within," Comparative Studies in Society and History 55 (2), 356-387.

Biobaku, Saburi, ed. (1965). The Egba and Their Neighbours, 1842-1872. Oxford: Clarendon Press.

Fage, J. D. (1958). An Atlas of African History. London: Edward Arnold Ltd.

Falola, Toyin. (1984). The Political Economy of a Pre-Colonial African State: Ibadan, 1830-1900. Ile-Ife: The University of Ife Press.

Falola, Toyin. (1992). "Warfare and Trade Relations Between Ibadan and the Ijebu in the Nineteenth Century." In: Toyin Falola and Robin Law, eds. Warfare and Diplomacy in Precolonial Nigeria. Madison: African Studies Program University of Wisconsin-Madison,  26-30.

Fenske, James. (2012). "Land Abundance and Economic Institutions: Egba Land and Slavery, 1830-1914." Economic History Review 65 (2), 527-55.

Fenske, James, and Kala, Namrata. (2017). "1807: Economic Shocks, Conflict and the Slave Trade." Journal of Development Economics 126, 66-76.

Folayan, Kola. (1967). "Egbado to 1832: The Birth of a Dilemma." Journal of the Historical Society of Nigeria 4 (1), 83-95.

Folayan, Kola. (1980). "Trade Routes in Egbado in the 19th Century." In: I. A. Akinjogbin and S. O. Osoba, eds., Topics on Nigerian Economic and Social History. Ife: University of Ife Press, 81-3, 100-2.

Law, Robin. ([1977] 1991). The Oyo Empire, c. 1600 - c. 1836: A West African Imperialism in the Era of the Atlantic Slave Trade. Brookfield: Gregg Revivals.

Law, Robin. (1978). "The Career of Adele at Lagos and Badagry, c. 1807 – c. 1837." Journal of the Historical Society of Nigeria 9 (2), 35–59.

Law, Robin. (1992). "The Oyo-Dahomey Wars, 1726-1823: A Military Analysis." In: Toyin Falola and Robin Law, eds., Warfare and Diplomacy in Precolonial Nigeria. Madison: African Studies Program University of Wisconsin-Madison, 9-25.

Law, Robin. (1994). "Dahomey and the North-West." Cahiers du Centre de Recherches Africaines 8, 149-67.

Law, Robin. (2004). Ouidah: The Social History of a West African Slaving ‘Port’ 1727-1892. Athens: Ohio University Press, 2004.

Lovejoy, Paul E. (2016). Jihād in West Africa during the Age of Revolutions.Athens: Ohio University Press.

Mabogunje, M. A., and Omer-Cooper, J. (1971). Owu in Yoruba History. Ibadan: Ibadan University Press.

Mouléro, Thomas. (1965). "Guézo ou Guédizo Massigbé." Etudes dahoméennes 4 (5), 51-92.

Nunn, Nathan. (2008). "The Long-Term Effects of Africa’s Slave Trades." The Quarterly Journal of Economics 13367, 139-76.>

Parrinder, E. G. ([1956] 1967). The Story of Ketu: An Ancient Yoruba Kingdom. Ibadan: Ibadan University Press.

Sequeira, Sandra, Nunn, Nathan, and Qian, Nancy. (2017). "Migrants and the Making of America: The Short- and Long-Run Effects of Immigration during the Age of Mass Migration." CEPR Discussion Papers (2017), 1-49.