I do not know about a national directory and would like to know, if there is one.
In the Sacramento area, I can recommend the Mark J RV Park on Madison Ave. just one block off of I-80.
It started out as a senior mobil home park many, many years ago and has gradually switched over to RVs. It's probably 2/3 or 3/4 RVs now. It's a very clean park, landscaped, quiet (provided you're not right up front by the six lane Madison Ave.) with 50 amp pedestals. So if you have a 30 amp rig you'll need the adaptor.
The Mgr. is a nice guy and so are the other guests...just very friendly. The spaces are wide. While the rig sits on a rock bed and sits between the asphalt driveway on the back side and a large concrete slab patio on the front side makes it very easy to back in to. You also have the wide streets that mobil home parks of years ago used to have. This place is very well maintained and quiet.