This article examines the influence of local alcohol prohibition on the prevalence of methamphetamine labs. Using multiple sources of data for counties in Kentucky, we compare various measures of meth manufacturing in wet, moist, and dry counties. Our preferred estimates address the endogeneity of local alcohol policies by exploiting differences in counties’ religious compositions between the 1930s, when most local‐option votes took place, and recent years. Even controlling for current religious affiliations, religious composition following the end of national Prohibition strongly predicts current alcohol restrictions. We carefully examine the validity of our identifying assumptions, and consider identification under alternative assumptions. Our results suggest that the number of meth lab seizures in Kentucky would decrease by 35% if all counties became wet.