From the summary:
Public libraries in the State of Texas provide significant economic benefits for their communities. This report examines these economic benefits, and documents those activities which contribute to economic activities throughout all regions of Texas. In 2011 Texas public libraries collectively were found to provide $2.407 billion in benefits while costing less than $0.545 billion, a return on investment of $4.42 for each dollar invested.
Appendix C (scroll down) contains:
Summaries of Prior State and City Impact Studies
States: Colorado, Florida, Indiana, Pennsylvania, South Carolina, Wisconsin
Cities: Charlotte, Philadelphia, Seattle, Consortium of Southwestern Ohio Municipalities