In this paper, I study the long-term effects that temporary upstream tariffs have on downstream industries. Even temporary tariffs can have cascading effects through production networks when placed on upstream products, but to date, little is known about the long-term behavior of these spillovers. Using a new method for mapping downstream industries to specific steel inputs, I estimate the effect of the steel tariffs enacted by President Bush in 2002 and 2003 on downstream industry outcomes. I find that upstream steel tariffs have highly persistent negative impacts on the competitiveness of U.S. downstream industry exports. Persistence in the response of exports is driven by a restructuring of global trade flows that does not revert once the tariffs are lifted. I use a dynamic model of trade to show that the presence of relationship-specific sunk costs of exporting can generate persistence of the magnitude that I find in the data. Finally, I show that taking both contemporaneous and persistent downstream impacts into account substantially alters the welfare implications of upstream tariffs.