Hundreds of grocery outlets needed across the United States to achieve walkable cities.

The location of amenities in urban areas fundamentally shapes both sustainability and equity outcomes. While cities worldwide are pursuing walkable neighborhood initiatives, the practical implications of retrofitting existing urban areas remain unclear. How many new facilities are needed, and where should they be located to ensure equitable access? We analyzed supermarket access across 500 U.S. cities using an optimization approach that minimizes both average distance and inequality in its distribution. Unlike traditional methods that focus solely on reducing inequality or average distance, our approach identifies solutions that improve overall accessibility while reducing disparities. We found that 25% of cities could achieve 15-minute walking access by adding five or fewer stores in optimal locations, while more ambitious 5-minute targets would require over 100 additional stores in most cities. These findings demonstrate both the potential for strategic interventions to efficiently improve access and the substantial challenge posed by car-oriented urban development. By identifying priority areas for new facilities while considering distributional impacts, our method can inform multiple stakeholders working to create more sustainable and equitable cities - from local governments using zoning and incentives to state agencies developing funding programs and community organizations advocating for improved food access.