Differences in rapid increases in county-level COVID-19 incidence by implementation of statewide closures and mask mandates — United States, June 1–September 30, 2020

•Nationwide data on effect of community mitigation policies on COVID-19 incidence are limited.•U.S. counties in states that closed for <60 days were more likely to have rapid increases in COVID-19 rates.•U.S. counties in states with mask mandates were 43% less likely to have rapid increases in COVID-19 rates.•Effects of mitigation measures are greater in less urban counties.•Statewide mask mandates and longer closures could help limit COVID-19 incidence.