I am currently at Woodhead Park along the Brownlee Reservior in Hell's Canyon. It is a well-maintained park owned and managed by Idaho Power. There are 124 RV sites, all with water and electric. The park is popular with fishermen and folks who like playing on the water; I saw a lot of trucks pulling campers that were pulling boat trailers (you can do that here). The park is inexpensive-- $16 per night, $14 per night if you are 60+, so I got to use my first-ever senior camping discount. The maximum stay is fourteen days. There are four camping loops and at least two bathroom / shower facilities, maybe three. There are a few sites for tent campers.
On the downside, summertime is hot. Most of the time I've been here the high was in the low 90s, but it was 103F today. A breeze picks up in the afternoon, but 103 is 103. Fortunately our Escapes have good A/C units. Also, the park is remote. There is a convenience store three miles away, but the nearest settlement of any size is thirty miles away, in either direction: Cambridge, Idaho or Halfway, Oregon, and those towns have only a few hundred people. Access is by one of those twisty turnie mountain roads that might make flatlanders like me a bit nervous.
Here is a link and some photos.