...but the first thing that came to mind when I saw the topic was Nancy Drew.
I read the Nancy Drew books when I was younger. And reread. And reread again. All fifty-six original yellow-bound Nancy Drew books are still on my shelf, and I can still name the plots of most of them, and rattle off my favorites. (In case you're wondering, a few of those favorites are the Ghost of Blackwood Hall, the Spider Sapphire Mystery, and the Secret in the Old Attic :)
I loved all of the characters--like tomboyish George, shy Bess, fussy Hannah, logical Carson, and chivalrous Ned--but Nancy was the best, and rightly the leading lady. She wasn't a Lois Lane or MJ Watson waiting to be rescued by a superhero, she was the super hero. (Hmm...does that make Ned Lois Lane?)
The way Nancy solved each case, more efficiently and daringly than the police or male detectives, made her a strong character. The books were set in a time when women were still expected to cook and clean. Nancy didn't. When I was younger, I knew I wanted to be as strong of a person as Nancy.