KEYSTONE, South Dakota — The only thing tiny about the size of this town, nestled in a valley in the Black Hills Mountains, is its 3-square-mile footprint, located a couple of miles below the ascent to Mount Rushmore.

As during most days that do not include snow, it was packed last week, with people sitting outdoors, eating at restaurants or pubs, shopping at local shops, or stocking up on bottled water for the last stop before their final destinations.