We provide theory and evidence on the contribution of slavery wealth to Britain’s economic development prior to the abolition of slavery in 1833. We combine data on individual slaveholders from compensation records, an exogenous source of variation in slavery wealth from weather-induced shocks to mortality of the enslaved during the middle passage, and a quantitative spatial model. Exogenous increases in slavery wealth reduce the agricultural employment share, increase the manufacturing employment share, raise the number of cotton mills, and increase property values. Quantifying our model, we find that slavery wealth raises aggregate income by the equivalent of around a decade of economic growth and increases local income in places with the greatest involvement in slavery by more than 40 percent.