This document summarizes a philanthropic effort called the City Accelerator. The City Accelerator is a $3 million, 3-year program that will work with cities in 3 cohorts over 18 months each to address challenges like building a culture of innovation and improving civic engagement. It will provide coaching, technical assistance, and resources to help cities design experiments and share best practices through municipal guidebooks. Eligible cities are members of the Project on Municipal Innovation and will apply and present ideas to be selected for the program. The goal is to bring together different sectors to address major problems and achieve large-scale results.