This paper 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, we document that the amount of intercity investment between a pair of cities increase by 45% with the introduction of an HSR line connecting the cities. We enhance the causal inference by applying high-dimensional fixed effects, and focusing on city pairs that are ¡°accidentally¡± connected in the network. The HSR effect is the strongest in industries that require on-site monitoring, as well as for controlling stakes in large distant investments.