Opening up neighborhoods that offer greater opportunities for social mobility to low- and moderate-income households remains a challenge in the United States. Exclusionary zoning practices act as a barrier to current efforts by restricting the supply of affordable housing. In this paper, we examine whether fair share policies that seek to bypass these restrictive zoning practices offer one potential solution. Focusing on Massachusetts Chapter 40B, we find clear evidence that such policies build affordable housing in neighborhoods with strikingly greater opportunities for social mobility than are otherwise available to low- and moderate-income households. Leveraging novel data on 40B development addresses linked to a wide range of public and administrative records, we find that 40B produces affordable units in neighborhoods with greater economic mobility, higher performing schools, greater social capital, less pollution, better health outcomes, and lower incarceration rates than both the typical neighborhood in Massachusetts and those available to beneficiaries of the state’s Low-Income Housing Tax Credit, Housing Choice Voucher, and public housing programs. Consistent with previous research on policies that have segregated affordable housing and opportunity, we also find that neighborhoods with affordable 40B units are whiter and more affluent than average. An examination of underlying policy mechanisms suggests that 40B’s ability to bypass exclusionary zoning plays a central role in explaining differences in neighborhood characteristics between 40B and other programs. We further find little evidence to support concerns that 40B’s zoning override leads to affordable 40B units being built in the least advantaged areas of municipalities, in polluted zones, or near highways, though a non-trivial share of units are located in industrial zones. These results suggest that policies like 40B may be valuable complements to other major housing programs in the United States.