Although a large body of quantitative environmental justice research exists, only a handful of studies have examined the processes by which racial and socioeconomic disparities in the location of polluting industrial facilities can occur. These studies have had mixed results, we contend, principally because of methodological differences, that is, the use of the unit-hazard coincidence method as compared to distance-based methods. This study is the first national-level environmental justice study to conduct longitudinal analyses using distance-based methods. Our purposes are to:(1) determine whether disparate siting, post-siting demographic change, or a combination of the two created present-day disparities;(2) test related explanations; and (3) determine whether the application of distance-based methods helps resolve the inconsistent findings of previous research. We used a national database of commercial hazardous waste facilities sited from 1966 to 1995 and examined the demographic composition of host neighborhoods around the time of siting and demographic changes that occurred after siting. We found strong evidence of disparate siting for facilities sited in all time periods. Although we found some evidence of post-siting demographic changes, they were mostly a continuation of changes that occurred in the decade or two prior to siting, suggesting that neighborhood transition serves to attract noxious facilities rather than the facilities themselves attracting people of color and low income populations. Our findings help resolve inconsistencies among the longitudinal studies and builds on the evidence from other subnational studies that used distance-based methods. We conclude that racial discrimination and sociopolitical explanations (ie, the proposition that siting decisions follow the'path of least resistance') best explain present-day inequities.