Over the past twenty years, research on the vulnerability of human populations to various hazards has dramatically increased. Analyses and maps of vulnerability can help emergency managers, decision makers, and stakeholders identify locations that need the most attention in hazard mitigation efforts. However, most assessments have been highly localized or have been performed at an insufficient spatial resolution. This study utilizes a geographic information system (GIS) to evaluate the vulnerability of human populations to meteorological and climatological hazards in the contiguous United States at the county level. Knowledge of both the likelihood of hazards and the socio-economic factors in a particular location are necessary to effectively quantify vulnerability. Climatologies of nine different hazards are combined with a modified version of the Social Vulnerability Index (SoVI) to create composite vulnerability scores for each county. The SoVI uses socio-economic data mainly drawn from the U.S. Census. The SoVI uses principal components analysis to objectively convert a relatively large number of socio-economic variables into a much smaller number of components. These new components represent broader social themes that are combined to determine the relative social vulnerability across counties. Improvements to methods of working with hazard and socio-economic data are presented. Additionally, resampling techniques are used to estimate the stability of the vulnerability scores.