If US government shuts down, NPs will largely remain open with skeleton ranger crews, no services
With concerns growing that the federal government will shut down, at least partially, late this week, the question of whether the National Park System will be open to visitors is a natural one. The answer is yes, but with some caveats.
If government does close, most National Park Service employees will be sent home, or furloughed, for the duration of the closure. Key personnel, such as law enforcement rangers and those needed to keep the power on to buildings will remain on the job. Concessions will continue to operate, and visitors will be free to enter.
https://www.nationalparkstraveler.org/2018/12/will-national-parks-be-open-if-government-shuts-down