This article investigates how transportation networks shape firms' geographic footprint by reducing monitoring costs of distant investments. Exploiting the staggered expansions of China's passenger high-speed rail (HSR) network, the authors document that the amount of intercity investment between a pair of cities increases by 45% with the introduction of an HSR line connecting the cities. They enhance the causal inference by applying high-dimensional fixed effects, and focusing on city pairs that are "accidentally" connected in the network.