The rest area at the SD/MN boarder has been rebuilt. It has been under construction for a couple years and the new facility looks really nice. The building itself isn't open yet nor is the landscaping in. That work will be completed Spring 2020. I will post updates to the cache as work progresses. The parking area is open!
SD is divided north/south by the Missouri River. As you head west from here you will cross the river at Chamberlain wihich is about 150 miles. At that point you will cross over into what is known as West River. West River is made up of a lot of wheat fields, grazing areas and some not so good land. Part of it is called the Badlands. The old joke goes "I have been driving across SD from the MN boarder and after three hundred miles there is a sign - Badlands Next Exit - well, what have I've been driving in for the past 300 miles?" All the way west are the Black Hills.
The cache container is a simple ammo can for now. I will upgrade it and stock it better. I will post updates as that happens.
Enjoy your time in South Dakota.