In this paper, we use a unique historical event, the creation of the early internet, the ARPANET, to unveil the mechanisms underlying knowledge production and innovation. ARPANET was introduced in 1969 and then connected many universities in the US. Initially conceived to share computing resources, the core of the network traffic consisted of emails, suggesting the network became a highway for communication. Tracking the publications of US universities, we use an event study difference-in-difference analysis to draw causal evidence on the effect of accessing the network on knowledge production. We show that accessing the network substantially increased the productivity of researchers: with more publications, publications in top journals, and also more collaborations with other connected universities. The main driver of productivity growth, however, was not the facilitation of formal collaborations between institutions. Indeed, additional collaborations accounts for only one tenth of the total increase in productivity. We further evidence that collaborations between connected universities did not span a longer distance. On the other hand, the average age of references contained in the publications significantly decreased, but only for references to the works of other connected institutions. Overall, our results suggest that access to knowledge was the main driver of productivity growth.