To kick off national park week, the National Park Service is offering free entrance on the first day to celebrate.
National park week begins April 16 and ends April 24.
The NPS waives the entrance fee to any park only five days out of the year, including Veterans Day and Martin Luther King Jr.'s birthday.
The agency says the fee-free days allow those to visit more than 400 parks that typically charge an entrance fee.
Some parks are free all the time.
The agency says visitors will still be responsible for amenity or user fees for activities including camping, boat launches, transportation, or tours.