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Winnie Winkle was one of the first of many "working girl" comic strips that came out of the 1920s, and was certainly one of the most popular. It ended up running for an impressive 76 years, and spawned a series of Dell comic books and even a few movie shorts. It was even one of Roy Lictenstein's major influences.
This strip in particular shows off cartoonist Martin Branner's simple but elegant style, with some brilliant crosshatching in the trees. I'm also a big fan of the lettering. So many cartoonists of this era were horrible at it, but the text here is very clear and easy to read.
And of course I love the joke.