NPS Rangers and US Park PD are on their own system together. (Well, it's GGNRA, but I'm not 100% certain if both are on there...I think it's both). Someone who lives there will be able to definitively tell you.
Thanks for the info on the Park Police. I'm mainly interested in the FPS, aka Federal Police, the police for federal properties, like the SSA, and the fed bldg. They used to be in the 41X.XXX Mhz band with the FBI and whatnot back in the day.
The FPS is on 417.700 in San Francisco. Most of the traffic is San Francisco related but you'll occasionally hear them in the Easy Bay checking on Federal buildings there.
As Bill wrote, the Park Police and almost all the federal Park Rangers are on the GGNRA trunk system listed in the RR database. The only exception is Point Reyes National Seashore, which isn't technically part of the the GGNRA. They are on 170.050 but even the rangers there tend to operate on the GGNRA trunk system more than the VHF system so most of the traffic is admin stuff like parking out at the lighthouse.