This interactive, designed and built by Slate’s Andrew Kahn, gives you a sense of the scale of the trans-Atlantic slave trade across time, as well as the flow of transport and eventual destinations. The dots—which represent individual slave ships—also correspond to the size of each voyage. The larger the dot, the more enslaved people on board. And if you pause the map and click on a dot, you’ll learn about the ship’s flag—was it British? Portuguese? French?—its origin point, its destination, and its history in the slave trade. The interactive animates more than 20,000 voyages cataloged in the Trans-Atlantic Slave Trade Database. (We excluded voyages for which there is incomplete or vague information in the database.) The graph at the bottom accumulates statistics based on the raw data used in the interactive and, again, only represents a portion of the actual slave trade—about one-half of the number of enslaved Africans who actually were transported away from the continent.
There are a few trends worth noting. As the first European states with a major presence in the New World, Portugal and Spain dominate the opening century of the trans-Atlantic slave trade, sending hundreds of thousands of enslaved people to their holdings in Central and South America and the Caribbean. The Portuguese role doesn’t wane and increases through the 17th, 18th, and 19th centuries, as Portugal brings millions of enslaved Africans to the Americas.
In the 1700s, however, Spanish transport diminishes and is replaced (and exceeded) by British, French, Dutch, and—by the end of the century—American activity. This hundred years—from approximately 1725 to 1825—is also the high-water mark of the slave trade, as Europeans send more than 7.2 million people to forced labor, disease, and death in the New World. For a time during this period, British transport even exceeds Portugal’s.
In the final decades of the trans-Atlantic slave trade, Portugal reclaims its status as the leading slavers, sending 1.3 million people to the Western Hemisphere, and mostly to Brazil. Spain also returns as a leading nation in the slave trade, sending 400,000 to the West. The rest of the European nations, by contrast, have largely ended their roles in the trade.
By the conclusion of the trans-Atlantic slave trade at the end of the 19th century, Europeans had enslaved and transported more than 12.5 million Africans. At least 2 million, historians estimate, didn’t survive the journey. —Jamelle Bouie
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Correction, June 30, 2015: The interactive originally displayed incorrect locations for Quilimane (also spelled Quelimane), Malembo, and Cardenas. They are in Mozambique, Angola, and Cuba, respectively, not Sudan and Spain. Furthermore, the map had located a port called “Spanish Americas” in eastern North America. The revised map does not show this port or voyages to it.
Correction, June 25, 2015: The interactive originally displayed incorrect locations for St. Vincent and Zion Hill. They are in the Caribbean, not in the U.S. and Canada, respectively.
Andrew Kahn is Slate’s assistant interactives editor. Follow him on Twitter.
Jamelle Bouie is a Slate staff writer covering politics, policy, and race.