In the period between the 1830s and 1850s, Marseille’s merchant navy experienced major change: a progressive transition from a free, clean and renewable but irreg- ular energy source —the wind— combined with a tried-and-tested technology and well-developed training system, to a costly, cumbersome and polluting fossil fuel —coal— relying on a high-potential, complex and expensive converter, the steam engine. We have chosen to revisit this key moment in the long history of the Port of Marseille in light of recent historiographic contributions to economic, maritime and environmental literature. Who were the stakeholders in this transition? What circumstances led them to take an interest in this new mode of maritime transport? With what investments? Which technological sector provided support? What kinds of resistance did they encounter? In addition to these questions, we also wanted to determine the consequences of these choices for traffic, practices, tools, operating areas and the environment of the Port of Marseille.