An intrinsic feature of a pre‐modern society is in its fragmentary markets. Fragmentary markets are more likely to fail in the coordination of resource allocation. However, if a concentrated market is exogenously formed and the market could provide the only price to local markets, the market can work as a pivot of coordination for development. Treaty port markets imposed on nineteenth‐century Japan worked as the pivot and ignited Japan's industrialization. We examine the silk‐reeling industry, which was the major export industry and which led to Japanese industrialization, and the role of treaty ports in its development.