Based on estimations, I think somewhere over 100 units.  By the way, we have also camped at Hunting Island several times although not in a TM.  We also first saw a TM at Edisto Beach State Park.

Last summer at a Sleeping Bear National Lakeshore campground (in northern lower Mich.), we camped adjacent to another Trailmanor. The other TM pulled in and had set-up before even noticing us there.  Now that doesn't happen too often.