Are there campsites that don't need a reservation if driving in late at night how do you pay for the campsite

In the summer months it's very busy very packed there during the winter months it's much easier but just as you enter there they do have a pay station even late at night you can pull in and pick up the envelope drive out to a space and pay in the morning

Elderberry flats, off of Evens creek rd Sams Valley, and Cook and Green by The Applegate just in the California side it's an old YCC camp

I am not sure as we didn't camp there.

You could always stay in the rest area which is at the entrance to the park.

Im not sure about reservations ut it fills up fast during the day and they have a pay station