Recent evidence suggests that minorities and low income families often bear a disproportionately large burden of. residential exposure to hazardous waste facilities in Los Angeles County. Debate over the origin of this pattern centers on two explanations. Proponents of the Environmental Justice movement hypothesize that the siting process for these facilities is discriminatory, with preference to areas with a high percentage of minority residents. Others have suggested that exogenous socio-economic factors often lead minority populations to be less risk-averse when making housing decisions. Using the ArcView GIS program with information from the U.S. Census and public records, this longitudinal study documents the changing demographics of a growing Los Angeles County. Preliminary results of this study favor the Environmental Justice hypothesis that many of these facilities were originally sited in a racially biased manner.