Last month, I drove I-90 in South Dakota in both directions between Wall and Mitchell, as well as the business routes I hadn't already covered. Most of the routes in the HB are signed. But I-90BS (White Lake) is unsigned, from both directions of I-90 as well as on the route itself and its intersections with side streets in White Lake.
The
AARoads Interstate Guide calls the White Lake spur "retired".
