To some, infill development still occupies a quaint niche in the world of city-building. But over the past few years, greenfield development on the urban fringes has gone fallow and a host of economic, social, and regulatory forces have made infill more viable. Attempting to lead that charge is the newly formed California Infill Builders Association, a professional group made up of established and aspiring infill developers who seek mutual support in their effort to bring new development to urban areas.