This primitive campsite is located along the middle fork of the Powder River west of Kaycee, Wyoming. I would suggest an AWD or 4WD vehicle to reach the site. This area of Wyoming is called Hole-In-The-Wall country, and Butch Cassidy and the Wild Bunch used to hide out in the vicinity. There are also some very nice pictographs nearby.
The campsite is free with a vault toilet and no other amenities -- no potable water, no wood, and no trash pick up. Haul out what you haul in. It can get very hot and windy here in the summer. So much so that I cut a two night trip short by one night. You have access to the middle fork of the Powder River, but it's about 800 feet below you as the campsite is on a canyon bluff.
The ghost town of Kirwin, Wyoming is approximately 34 miles southwest of Meeteetse, Wyoming. It is recommended you use a 4WD vehicle as you have to ford the Wood River twice with the last several miles being rocky jeep trail.
In the early 1900s it had a population of about 200 people who mined gold and silver, but an avalanche in 1907 destroyed several buildings and killed three people, so the town was abandoned later that spring. The US Forest Service has preserved many of the buildings in Kirwin, including informational/historical placards.
If I remember correctly, there are three "campsites" -- meaning three bear boxes. You are just outside of Yellowstone National Park, and grizzly and black bears frequent the area. Last I knew there is also a wolf pact in the area. The campsites are on unlevel and slanted ground, so it's best to camp on the gravel bars. While there is a vault toilet on site, there is no potable water. This is a very remote site at an elevation of 9,200 feet. But if you can make it there, it is well worth the trip.
The Medicine Lodge Archaeological Site is maintained by the Wyoming Game and Fish Department. I normally avoid campgrounds and prefer dispersed camping or backpacking, but I gladly camp here. Sites are well spaced out with Medicine Lodge Creek running through the campground. A walking/bike path goes end to end in the park following the creek. It does not have electrical hookups or dump stations for RVs. There are no shower facilities, but it does have vault toilets and drinking water. You can also buy firewood onsite as there is really nowhere to gather your own wood inside the park. You can go down the 4WD road at the north end of the park to Black Butte a bit and usually find your own firewood, however. All fires must be within the campsite fire rings.
The Medicine Lodge Archaeological Site is a perfect place to camp to explore the Bighorn Mountains, being relatively close to the Medicine Wheel and Shell Falls. If you enjoy craft beer, Tensleep Brewery -- located in a refurbished barn -- is located approximately 20 - 30 miles south in Tensleep.