During the “steam century” between 1830 and 1930, major political and economic entities in Europe, Asia, and the Americas became increasingly connected by steam navigation and railway transportation. Against this global backdrop, steam navigation was established and became regular on the formidable Upper Yangzi River in China between the 1870s and the 1920s. This breakthrough hinged on developments in the methods of tackling rapids (tan) – fierce and unpredictable currents descending like small waterfalls. Previous studies have mostly focused on how agents of the British Empire and other imperial powers tried to solve such constraints in steam navigation through charts, sailing directions, and other initiatives to make the Upper Yangzi riverscape legible. Incorporating previously unused archives, this article highlights how local environmental and social conditions shaped the steam shipping system on the Upper Yangzi River. This article argues that rapids, as well as local boatmen's experiential knowledge of them, propelled British and other foreign agents to transform their ways of organizing steam shipping in terms of vessel design, crew recruitment, and infrastructure allocation. More broadly, this article exemplifies the need to look beyond imperial agents and employ more locally situated perspectives to explain the technological developments underlying the modern world.