This article analyzes why the San Diego-Tijuana city system has undergone a process of supply chain urbanism—development in the logistics sector—since 2013. The article compares the 2003–2013 period, during which the region saw a lack of growth in the transportation and warehousing sector, with the 2013–2023 period, when the sector underwent regionally specific growth at unprecedented rates, measured through increases in employment and cross-border commercial traffic. It is argued that changes in trade law and trade relations, global/transpacific supply chain contingencies, and transnational planning and infrastructure investments have led to supply chain urbanism in San Diego-Tijuana. Due to contingencies in transpacific supply chains, it is argued that the region has developed a new logic of warehousing, moving from a just-in-time model to a just-in-case model. Lastly, the article comments on the effects of supply chain urbanism in the region.