This research report presents methods used to conduct a national assessment of access to nutritious, affordable food in low-income neighborhoods and communities, an initiative contained in the 2008 Farm Bill. A number of research challenges were addressed in carrying out this directive, including defining what constitutes likely food sources that are nutritious and affordable; identifying low-income neighborhoods and communities; and developing criteria for measuring levels of access to nutritious, affordable food. To address these challenges a national store directory was developed; GIS methods including a projection of Census population data to uniform square-kilometer grids were applied. Cumulative density functions were used to describe the relationship between the share of a given population group, such as urban-low-income, and its distance to the nearest supermarket. Maps of selected areas were used to describe differences in food access in low-income areas.