Euclidean zoning predicates the separation of land uses with negative externalities, such as manufacturing and intense commercial uses (referred to as “High Intensity uses”), from residential districts. In practice, High Intensity uses often lack adequate buffering and can have deleterious health and economic effects on nearby populations. These include high levels of pollution, noise, traffic and low land values. Some believe that zoning practice locates High Intensity districts disproportionately nearby residential areas housing low-income households and people of color, generating disparate impact. Yet, this area has remained understudied, lacking a systematic examination beyond small case studies. This study remedies this gap by positing: In US cities, High Intensity zoning occurs with greater frequency near predominately low-income or non-white census tracts. If this phenomenon is true, zoning would disproportionately impact those populations. It suggests residential zoning distributions, historic redlining practices, and the historic framework of zoning adoption reflect this relationship. Four phases employ GIS and statistical analyses of zoning maps, ordinances, historic archives, and demographic data in 13 cities to test this hypothesis. The study concludes with recommendations for re-positioning planning priorities by adopting environmental justice policies to remediate disparate impact.