As Yellowstone and other national parks end a two-month shutdown due to the coronavirus, park officials want visitors to take precautions, such as washing their hands, keeping a safe distance from other people and wearing masks in public.
It's unclear whether tourists who often disobey park rules will comply.
If not, popular national parks known for drawing shoulder-to-shoulder summer crowds could become the next U.S. hot spots.
Park officials say they plan is to let folks guard themselves against COVID-19, just as they do for the usual national park dangers that range from altitude sickness to grizzly bears.