I also wanted to mention that the caboose baby, who is a boy, has totally latched on to Betsy-Tacy in a way that surprised me. I’m not sure why I thought of Lovelace’s books as "too girly" when I didn’t think twice about Laura Ingalls Wilder for him, but they are not and in many ways they are even more relevant to this generation than they were to my older kids.
There is a very long storyline in "Betsy and Tacy go up the Big Hill" involving a Syrian refugee girl who is teased for more or less the same reasons Syrian refugee girls still get teased 117 years later. Racism is not ignored, but it is never portrayed as acceptable. Betsy notices and questions when Tib’s father compliments a little brother on building a play house and tells him he will grow up to be an architect but that Tib, who put every bit as much effort and creativity into the house, "will grow up to be a housewife".
The girl Lovelace based Tib’s character on probably did, but the Ray family was supportive of Betsy’s older sister’s plans for a career before marriage and of education and travel for both daughters and the author obviously wanted to point out that sexism is not acceptable or "just the way things were".
Betsy’s parents are a bit more free range than Ma and Pa Ingalls and the girls are comfortably middle class, but there is a similar sense of love, warmth, acceptance, and family loyalty.
The series follows Betsy from before her fifth birthday up until marriage and young adulthood. I made ds do the math for me but if Grace Ingalls was born when Laura was fifteen then Betsy is eight years younger than Grace and 20 years younger than his great-grandmother, who wrote children’s stories that are no longer in publication.
If you’re just looking for historical fiction for a particular period, that means that they take place at the tail end of the 19th century and the very beginning of the 20th. They were originally written as bedtime stories for the author’s late life baby. She was an established author for adults at the time. She wrote during the 1940s and IIRC, Wilder wrote in the 30s.
Will edit and/or update if this inspires my not-history buff to any interesting rabbit trails.