The economics literature on Atlantic slavery attests to its negative long-run impact on development outcomes in Africa and the Americas. What was slavery’s impact on Europe? In this paper, I test the hypothesis that slavery contributed to modern economic growth in Europe using data on European participation in the Atlantic slave trade. I estimate a panel fixed effects model and show that the number of slaving voyages is positively associated with European city growth from 1600-1850. A 10% increase in slaving voyages is associated with a 1.2% increase in port city population. Using a newly created dataset on British port-level trade, I show that for the UK, this effect is distinct from that of general overseas trade, which also increased during this period.