Just looking at her photos, I see how physically strong & durable Frances was in her youth.

From what I've read, she liked the outdoors as much as she liked reading, the Greek ideal of a healthy mind in a healthy body, though some would later dispute that she had a healthy mind.

She would go off camping by herself and I read somewhere that she was a very strong swimmer, which she demonstrated out in the Pacific during the filming of one of her movies.

She was brought up that way, in an American age when, in the absence of the electronic entertainments of dubious value to today's youth, the outdoors was a natural venue for young people. There, they enjoyed their leisure and learned the land, as Frances did.

So it's not surprising that this independent loner, physically & intellectually strong, made a cross-country motor trip by herself in 1940 from NYC to the California coast before the age of the interstates. That trip, at that time, would have been fascinating.