We stayed here when we where at Glacier because it was ruffly equal distance between the entrances. No sewer, but they come around and pump out your tanks. http://www.glaciermeadowrvpark.com/ It's mostly an open field with woods on the back side.
Stayed here the last time in West Yellowstone
http://www.yellowstoneholiday.com/. Was a nice area if you want something with more of a view.
We do a lot of hiking when in these area's, so sometimes it's nice to have place to sit for a day. Not retired yet so we tend to over do it, but getting better at that.