Zoning determines what can be built where, and is ubiquitous in the United States. Low-density residential zoning predominates in US cities far more than in other countries, limiting housing opportunities for those who cannot afford large homes. These zoning regulations have racist and classist origins, make housing more expensive, and reinforce segregation patterns. While sociologists study these consequences of zoning, and other causes of unaffordable housing and segregation, they rarely examine zoning itself. This article argues for a sociological research agenda on zoning and land use.