We compile a novel high-frequency, detailed geographic dataset on mass layoffs from U.S. state labor departments. Using recent advances in difference-in-difference estimation with staggered treatment, we find that locally-mandated stay-at-home orders issued March 16–22, 2020 triggered mass layoffs equal to half a percent of the population in just one week. Our findings contribute to explanations for why job loss in 2020 was catastrophic, yet temporary.