Development of a rural-urban classification system for public health research that accommodates structural differences between states.

Rural environments in the United States present challenges to wellness, but there is a lack of tools with which to categorize rurality at the subcounty level. The most common tool, the Food and Drug Administration's 2010 Rural-Urban Commuting Area (RUCA) codes, uses data that are over a decade old and cannot accommodate regional differences in rurality. The purpose of this study was to develop a census-tract classification system of rurality and demonstrate its use in describing HIV outcomes.