Using data on the geographic location of fracking wells in four U.S. states with mandatory disclosure between 2011 and 2013 — Colorado, Oklahoma, Pennsylvania, and Texas — this paper analyzes the socio-demographic characteristics of people living close to fracking activity. Geo-coded well data from the FracFocus registry are merged to blockgroup-level socio-demographic data from the 2006–2010 American Community Survey and population density and land use data from EPA's Smart Location Database 2010. Different buffer zones around fracking wells are applied to capture effects at different spatial scales and to compare only areas with similar geological properties. We explain the distance to the nearest well within a county with fracking activity or within a buffer zone by race/ethnicity, income, educational attainment, various land-use control variables, and county fixed-effects. We find robust evidence that minorities, especially African Americans, disproportionately live near fracking wells, but less consistent evidence for environmental injustice by income or educational attainment. Strong heterogeneity across states can be observed, suggesting that an improvement in disclosure laws in other states, that would make similar analyses possible, is of great importance.