I’ve come across this map a few times now.
It started life as a thread on the iRV2 Newmar Owner’s Forum. A very long and, at times, somewhat controversial thread that is now over 40 pages.
The premise of the thread was for Newmar owners to share their experiences at RV parks that were Class A restricted and RV parks that were well suited for Class A rigs.
People look for different experiences when they go out with their rigs. We have stayed at all sorts of different places: driveways, fields, KOAs, casinos, parking lots, rustic RV parks and luxury Class A restricted RV parks. We enjoy the Class A parks when we are staying in one place for a month or longer.
The Class A RV Map page, to the extent that it will continue to be maintained, is another resource we will use when looking for an RV park that offers a good experience for Class A rigs. It differs somewhat from the US RV Big Rigs site. That site is a commercial undertaking and you have to pay to get access to their data. We have their book and, for the most part, we use the book and the site to see if our rig will fit in a particular campground. And, of course, there is always RV Park Reviews. Like many crowdsourced review sites, you have to use a bit of discernment when reading through the comments.
The folks behind the Class A RV Map produced this video which provides more insight into their volunteer effort.