Grassy Lake Road Campsite #8

This is free camping between Yellowstone and Grand Tetons, the sites are very dispersed with toilet facilities, picnic table, and a fire ring.
We stayed in site #8, miles down the well maintained gravel road.
Swarms of mosquitos in a biblical proportion. They descended on us like a blanket, repellent was marginally effective.
Rangers are very strict about utilizing the bear box, we left our portable shower out and it was considered water storage and was sequestered in the bear box (located on site).
Shared our site the second night with a couple in a van, plenty of room if you had a group with a few vehicles.

Apparently the huge fire in 2016 is still causing problems, as most of the campgrounds were closed due to fire. Campground #2 had two sites, both full, and #5 (actually the sixth campground we encountered) only had one site. All others were closed, and we ended up sharing a gravel parking area with two other families and about 5000 mosquitoes. The closed sites still had intact vault toilets, bear boxes, and picnic tables, but they were cordoned off for official use only. I hope the forest service will quickly reinstate these beautiful sites right on the river.

There is a large sign for the Headwaters Ranch on Flagg Ranch Road. Turn onto Flagg Ranch Road and then follow it to the right past the trail rides stable and continue until you find a campsite that is actually open. This is directly between Yellowstone and Grand Teton, at a time when all of Yellowstone is full as well as Colter Bay in Grand Teton. Go for free and uncrowded and skip staying at the parks.