Far more than just a typical interstate rest area, this stop along I-90 is part scenic overlook, part historic site, and part museum. The rest area's location on a bluff overlooking the Missouri River provides incredible views of the Valley below. It is also an official stop on the National Parks Service's Lewis and Clark Trail. There is a museum celebrating the journey of Lewis and Clark, including a replica 55 foot keelboat modeled after the one used during the exploration of the Missouri River. There is also a tourist information booth with info for about sites and stops throughout South Dakota
If you go:
Rest area is located on the South side of the Interstate, but it is reachable by travelers in both directions. Tourist Information desk closed in Winter.
Links:

I-90 Mile Marker 264
Chamberlain, South Dakota 57325 USA
Phone Numbers:
Information
+1 (605) 734-4562
+1 (605) 734-4562