I’ve been reading Hardy Boys books to my son lately. Before that it was Harry Potter, he watches Scooby Doo a bunch. There’s Nancy Drew and the Bobbsey Twins as well for other audiences.
Any notion what was the first teenage sleuth/crime fighter character?
Wasn’t “Robin” (of Bat Man and Robin) just a teen? Also, I had a series of mystery stories called “The Happy Hollisters” circa 1960’s…if anyone else might have read these books. But, I recall liking only the first one.
BTW: Your boy might enjoy Encyclopedia Brown stories, too.
Well, the Baker Street Irregulars come to mind, but they of course weren’t main characters. Our public library had a collection of Tom Swift Jr. stories. A quick search shows that they were first published in 1954. These aparently were a continuation of the Tom Swift stories, first seen in 1910. There was one copy of a Tom Swift Sr. story in our public library, but I didn’t read it, so I don’t know if it was a teen sleuth story or not. The first link google turned up was here
That’s the first thing I thought of, although there probably are others.
Hope it helps.
GES
Rover Boys - 1899
Bobbsey Twins - 1904, longest running series
Tom Swift - 1910
Hardy Boys - 1927
Nancy Drew - 1930
Encyclopedia Brown - 1963?
Three Investigators - 1964, the only licensed kid detectives 
There were dozens of others.
Jinx, I used to have a bunch of the Happy Hollisters books. I think they were originally my mom’s. The only one I remember involved them going to the Black Forest and seeing people make cuckoo clocks or something.