The car quit. It's the alternator, at least. I was lucky to have the car stop in front of a house, let alone people as welcoming as these. If it had died 10 miles later, I'd have really been in the middle of nowhere. The car quit Sunday afternoon and won't be running again until sometime Tuesday! These folks gave me the keys to their car and told me to go to the Fort Peck Interpretive Center!
I'll give a full report when this is all over.