We have stayed at Elkmont on several occasions. It is operated by the National Park Service. Amenities are limited but the restrooms and camp store are very good. You can run a generator during the day to charge batteries but not at night. The river is amazing and there are hiking trails there. Synchronous Fireflys in late May / Early June. Wonderful campground. Highly recommended. You can reserve 6 months in advance. Fills up quickly in the summer.