I have been to state campgrounds where they will charge a modest fee for
sanitary facilities use.  This way you can drive in to the facility.  A
lesser cost than a one day pass and well worth it if you are roughing it,
passing through.
Respectfully,
Steve

>Many State Campgrounds have showers and I have parked and used them many
>times without staying to camp.  Frowned upon, but they usually let you
>shower before they kick you out.