(In the 10 Betsy-Tacy books and 3 supplemental Deep Valley books, here's what I can think of off the top of my head: someone performs in blackface at a talent show, settler violence is alluded to a few times and an older character romanticizes "Indian wars", there are characters who are racist against Syrians living in town but the racists are in the wrong and that's the plot of "Emily of Deep Valley", and sometimes the antiracists are paternalistic against other cultures.)
Also to compare them to another series of a nearby time period, Betsy grows up but the books don't get dark like the Anne of Green Gables ones do. (There's understandable and sympathetic reasons for that and the Anne books are richer stories, but still...) It might be best to say that Betsy and Co. get to kind of stay in the Anne of Avonlea/of the Island period where it's mostly about the joy of new experiences and community.
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