After checking with three hotels in Chamberlain, SD, I learned that arriving at 11PM without a reservation is a bad idea as you get close to the tourist areas around the Black Hills.
Fortunately, the Bel Aire Mot(el) had a room for the low price of $55 — and worth that much. The nice desk clerk (who had a strong Jamaican accent, oddly), got out of bed to rent me a room. His good nature is behind the humor in the sign, I assume.
I was grateful for a place to sleep but recommend accommodations that have been remodeled since the 70’s if you can find them.