Local zoning regulations such as minimum lot size requirements and restrictions on the permitting of multifamily housing may exacerbate racial segregation by reducing in some neighborhoods the construction of units that could house prospective minority residents. Although this hypothesis has long been recognized by urban economists and other social scientists, the lack of uniform land use data across jurisdictions has made empirical progress difficult. Using detailed spatial data available for all municipalities in Massachusetts, I investigate the impact of density zoning regulation on location choices by race. Capitalizing on the geographic detail in the data, I focus on variation in block-level racial composition within narrow bands around zone borders within jurisdictions, mitigating omitted variable concerns that arise in studies focusing on larger geographic units. My results imply a large role for local zoning regulation, particularly the permitting of dense multifamily structures, in explaining disparate racial location patterns. Blocks zoned for multifamily housing have black population shares 3.4 percentage points higher and Hispanic population shares 5.5 percentage points higher than single-family zoned blocks directly across a border from them. A simulation based on these results suggests that equalizing zoning density regulation across the Boston metro area would lower segregation by half a standard deviation of the national distribution on the most common measure.