Social disparity in the spatial distribution of healthcare providers in urban areas is a recognized problem. However, efforts to quantify the problem have been hampered by a lack of satisfactory measurements and methods. We revive and enhance a strategy based on provider density, proposed nearly three decades ago. The method avoids the border-crossing problem associated with provider-population ratios, yet reports spatial accessibility in intuitive units that are easily compared across diverse populations and geographies. We find racial and socioeconomic disparities in our case city, Washington, DC, despite a citywide overabundance of primary care providers for children.