This article examines the large interstate variation in levels of unconventional gas development in the U.S. states. The following hypotheses are advanced to predict whether a state will be predisposed toward development: (H1) the availability of unconventional gas reserves; (H2) the availability of infrastructure to support development; (H3) a recent history of conventional oil and gas development; (H4) Republican party control of the Governor's office and state legislature; (H5) relatively low sensitivity to environmental issues; (H6) regulatory systems that treat UGD as a variant of conventional gas development; (H7) a pressing need for economic benefits as indicated by state and local measures of household income, unemployment and poverty; (H8) and public opinion supportive of development. To various degrees, each of the hypotheses is supported but important exceptions and surprises are uncovered in the qualitative and semi-quantitative analyses. Future research should continue the effort to explain the variation of development by expanding the geographical scope of inquiry and enlarging the sample of jurisdictions.