Salvador and Rio de Janeiro were the two largest slaving ports of the Americas, but they followed very different trajectories. Therefore, a comparison can shine a powerful light on the history of Atlantic slavery. This presentation will trace the transformations in the century and a half that culminated in the passing of the baton as largest slave port and capital to Rio de Janeiro, taking into account developments in European consumer markets, growth of internal market and political developments of the pluricontinental Portuguese monarchy, which increased its state capacity, even though it could never dispense with local allies. The lecturers will show that their role as major enslaving ports was not predicated only in their sugar hinterlands, because it was strongly linked to commercial networks that were increasingly both outside European control and escaping the grasp of the local slaveholding nobilities thanks to the rise of powerful local merchant elites.