STARS: 3.75 out of 5
ISLAND PARK DAM BOONDOCKING, IDAHO (NEAR WEST YELLOWSTONE ENTRANCE): GPS 44.4340, -111.3727
The rating is lower than I would otherwise give because the parking is a bit more challenging than I like. The boondocking spots are in a forest of trees, which is great for the ambiance and privacy, but makes maneuvering a bit harder. It is still very doable, but unless you are in a smaller rig, I'd recommend scoping it out before you drive in.
There are back ins and a few pull-throughs, but again, check it out first.
The lake is beautiful, although there were signs up about toxic algae which I guess appears in the summer. I called about it though before letting Avery swim in it, and the person I spoke to said that the sign was "left over" from the summer and not an issue at that time, which was the middle of May.
I don't have pictures of specific sites (sorry), but the photos here are of the lake access right near the boondocking spots.