This article explores the US contribution to the illegal transatlantic slave trade to Brazil and the tensions generated by this hemispheric connection in the mid-nineteenth century. It combines qualitative and quantitative approaches, based on diplomatic records and Voyages: The Trans-Atlantic Slave Trade Database, in order to assess the size and variety of forms of US participation in the traffic to Brazil. More generally, the article examines the tensions caused by the rise of abolitionism and the limits to the enforcement of anti-slave trade legislation in the free trade international environment that emerged after the Napoleonic Wars. By framing the attitudes of the US government within a broader Atlantic context, this work shows why certain forms of US participation in the contraband slave trade (such as providing US-built ships) became more predominant than others (such as directly financing and organising slave voyages) by the mid-nineteenth century.
