We study the interplay between transportation infrastructure, knowledge flows, and innovation. Exploiting historical data on planned portions of the interstate highway system, railroads, and exploration routes as sources of exogenous variation, we estimate the effect of U.S. interstate highways...

Large firms spawn spin-outs caused by innovations deemed unrelated to the firm's overall business. Small firms generate demand for specialized services that lower entry costs for others. We study the interplay of these two localized externalities and their impact on regional innovation. We...