I can only attest to the upper Mid-west area, and unknown if either of the planned trips so far intend to venture this far over.
There are state campgrounds likely available for the full year, although a power hook up may be the only amenity available during the so called non-camping winter months.
Further NW of me, in western North Dakota, everything commercial is full of folks living full time in their RV's because of the Bakken oil shale boom there. However, the aforementioned state parks should still be available in those same areas.
Once one gets north of say a Sioux Falls - Rapid City South Dakota line, or north of I-90, very few commercial campgrounds stay open, save for those already mentioned with Bakken traffic.
South of the line, I know places like the KOA in North Sioux City South Dakota is open all year long.
Best of luck and hope all have a great trip.
The Mad Norsky, Doll, Logan and Rocky
2014 Ram 3500 w/ Cummins/Aisin
2019 Northern Lite 10-2 EX CD LE Wet Bath
RV'ing since 1991
I took the road less traveled .....Now I'm Lost!