More and more local governments are embracing open data principles and releasing data online. The hope is that the greater transparency will engage residents, increase accountability, and spur new private uses of data. In Chicago, nongovernmental institutions have long provided data for community use and are now adapting their roles and services as new players and resources emerge. Understanding the rich local institutional and political context allows us to see the forces that shaped the impressive progress to date in open data and potential directions for the future.