This paper leverages the historical rollout of the Swedish railroad to identify the causal contribution of reduced communication and transportation costs to innovation and the emergence of a market for ideas. Between the mid-19th century and World War I, the Swedish state constructed the backbone of a more than 14,000 km long national network that connected previously isolated locations. Notably, the spread of the network coincided with a rise of innovative activity and trade in patents, which made Eli Heckscher (1941) term the period a “technological revolution” that marked Sweden’s transition to becoming one of the most innovative countries in the world. Crucially, the expansion of the Swedish railroad network also provides a unique setting to identify the causal impacts of transport infrastructure on the market for ideas and innovative activity.