One series that is lesser known and a bit hard to find is The Children of All Lands Stories by Madeline Brandeis. She and her daughter, Marie. This is what she writes in the preface:
“When I began to write these stories about children of all lands I had just returned from Europe whither I journeyed with Marie and Ref. Maybe you don’t know Marie and Ref. I’ll introduce them: Please meet Marie, my very little daugher, and Ref, my very big reflex camera.
These two are my helpers. Marie helps by being a little girl who knows what other little girls llike and by telling me; and Ref helps by snapping pictures of everything interesting that Marie and I see on our travels. I couldn’t get along without them.”
These are delightful stories written mostly in the 30’s. She wrote many including:
The Little Indian Weaver
The Wee Scotch Piper
Little Philippe of Belgium
The LIttle Dutch Tulip Girl, etc.
Another great series is the Twins series by Lucy Fitch Perkins. Many of these are now available as free ebooks and some are being reprinted.
Both of these series are wonderful and are valuable for geography/history/culture.