The COVID-19 pandemic may have altered visitation patterns to parks, with potential effects on human health. Little is known about park use early in the pandemic, how park availability influenced use, and whether park visits accelerated COVID-19 spread. Using weekly cell phone location data for 620 U.S. counties, we show park visits decreased by an average 26% between March 15 and May 9, 2020. Net of weekly trends, park visits were 2.2% lower when stay-at-home orders were in effect, yet increased by 8.4% with school closures and 4.4% with business closures. Park visits decreased less during the pandemic in counties where park availability was high. Levels of park visits were not associated with COVID-19 growth rate or incidence in the following weeks. Thus, parks served as recreation and leisure outlets when schools and businesses closed, especially where parks were more available, with no evidence of park use increasing COVID-19 spread. [ABSTRACT FROM AUTHOR]