looking for campground in NE New Jersey

We've been to Mahlon Dickerson Reservation a couple times, last time was 2016.

Excellent small campground with water and electric hookups and dump station.

Beaver Pond campground in NY would appear to be the closest at 15 miles and 27 minutes. Only a few RV sites and max length of 30'.

Mahlon Dickerson Reservation in Jefferson (small, Morris County Park, water/electric)
Great Divide Campground
Newburgh NY KOA
Liberty Harbor RV Park
Swartzwood State Park (no hook ups)
Spruce Run State Park (some water/electric)
Pleasant Acres Farm/Campground

Some of these are a bit of a drive, but I know of nothing close to USR – grew up and camp in NE NJ. You might find a Elks or such to boondocks but that's about it.

this is 35 miles from Upper Saddle River - Black Bear Campground

I have NOT stayed there, but it gets all 10's on the reviews

Here is an excellent resource to narrow your search:
Allstays Campground search by state and cities.