Drawing on lessons learned from cities trying to kick-start a new charter market, as well as from some of the most developed markets in the country, this report offers guidance for philanthropies on how to invest wisely as part of a city-based strategy. It also identifies potentially high-yield investments in the charter sector. This report is part of a three-piece series continuing the discussion from a National Charter School Resource Center/U.S. Department of Education conference exploring emerging city-based movements that embrace high-quality charters as an integral component of their reform strategy.