I-90 West Bound rest area about in the middle of the state of South Dakota. They have been in the process of rebuilding this rest area for the past couple years - they are finally done. Nice place to stop again.
Easy to get to and should be fairly easy to find. There is a funky gravel road that leads north out of the back side of the rest area. You only need to go a couple hundred feet on the gravel road then make a right and follow the fenceline.
The grass could get pretty tall.