We study a large-scale policy relaxing residential land supply constraints near major Dutch cities in the mid-1990s. Land allocation was determined centrally and was unrelated to pre-policy local market dynamics. Using administrative data, we explore effects on housing, mobility, and labor markets. New supply attracted high-income individuals, primarily from nearby high-income neighborhoods, where house prices decreased. New supply also increased local employment in surrounding areas, especially in high-earning occupations. We develop a rich quantitative spatial equilibrium model and show that the impact of relaxing supply constraints on housing markets and welfare crucially depends on job reallocation and on in-migration flows.