The latest spot to add to the list, as Frommer's reported would happen back in 2015: Muir Woods National Monument in Mill Valley, California, north of San Francisco.
Starting on January 16, 2018, each visitor who arrives to the 550-acre coastal redwood forest by car or shuttle will be required to have a reservation to be admitted. Those who arrive on foot or bicycle, however, will not need reservations.
In a press release announcing the change, the National Park Service says the purpose of the new system is to "address overcrowding, traffic congestion, and parking issues" caused by the 1.2 million people who visit the site each year.
The system is expected to launch January 1, after which visitors can make reservations up to 90 days in advance online or by phone for one of 232 parking spaces for $8 per vehicle or for a shuttle ride for $3 per passenger age 16 and older (younger kids will also need shuttle reservations, but they're free).
These charges will be required in addition to the Muir Woods admission fee of $10 for visitors age 16 and older—which means now tourists pay twice to see the woods, once to the government and once to a private vendor.
Visitors receive a specific arrival time once they successfully make a reservation, but they can stay as long as they want after being admitted.
For more information, including shuttle pickup times and locations, visit GoMuirWoods.com.