It depends on the park. Not sure of your area but we have been through this in Central Oregon and determined the following:
No caches in: Pilot Butte State Park and Fort Rock State Park.
Caches with permission in fee parks: certain areas are out and they would like some input for placement. Examples are Tumalo State Park and Smith Rock State Park.
Open for caching: no-fee and undeveloped state parks. Examples are La Pine State Park, Cline Falls State Park, and Robert Sawyer State Park.
Notes:
1. Certain areas are monitored and security measures are in place.
2. Where park grounds are close to private property, indicate a parking spot so that cachers will stay in the park when searching.
3. When in doubt contact State Parks.
Good luck!
We are near Coos Bay on the coast. The park we are thinking about is undeveloped with no fees. To be safe I will get in touch with the states park office, would hate to place it and then have it removed because I didn't do my homework.