Knowledge Access : The Effects of Carnegie Libraries on Innovation

Between 1883 and 1919, Andrew Carnegie donated approximately $1 billion in 2019 dollars to fund the construction of more than 1,500 public libraries across the United States. We show that this historical rollout of public libraries — which promoted access to knowledge for millions of people — increased the innovation output of recipient towns. To identify the causal effect of Carnegie libraries on innovation, we use new data on city-level patenting and a novel control group: cities that qualified to receive a library grant, applied for the program, received preliminary construction approval, but ultimately did not build a Carnegie library. Patenting in recipient towns increased by 8-13 percent in the 20 years following library entry. We show that this increase is concentrated in technology classes that overlap with library holdings.The number of women and immigrant inventors also increased after libraries opened. We provide evidence that additional access to scientific knowledge and opportunities to interact with fellow patrons are possible mechanisms