KOA offers park-model trailers, such as this one in Cloverdale, Calif., at 249 of its 475 campgrounds. "It's the fastest-growing part of our business," says Mike Atkinson, KOA's director of lodging.

Rebecca Miller shows a camp activity bag Friday in the office at Augusta Gardiner KOA campground in Richmond. Miller said that it is one of the changes they’ve had to make because of COVID-19.