The Rural-Urban Commuting Areas (RUCAs) were developed at the WWAMI RHRC in collaboration with, and with support from, HRSA’s ORHP and the Department of Agriculture. The RUCAs are a census tract-based classification scheme that utilizes the standard Bureau of Census Urbanized Area (UA) and Urban Place (UP) definitions with commuting information to characterize the nation’s Census tracts regarding their rural and urban status and relationships. The codes are based on whether a Census tract is located in a UA or UP and on the destination of its largest and second largest commuting flows. This project (1) produced and described the base 1998 demography of the RUCA code areas, (2) created quality state maps of the RUCA codes, and (3) has made this information and the codes easily available on the Web. The demographic description of the RUCA codes involved standard cross-tabulation analysis of the code areas nationally, regionally, and by state. Technical notes and maps are posted at www.depts.washington.edu/uwruca”>UW RUCA.