Aunt Jane's Nieces on the Ranch

Aunt Jane's Nieces at Millville is a young-adult novel by L. Frank Baum, written under the pen name Edith Van Dyne and the eighth book in the Aunt Jane's series. It revolves around Louise, her new baby, Jane and the ranch she and Arthur live on. The Ranch was built by a Spanish lord and contains secret passages within some of the walls.
L. Frank Baum was an author of children's books, best known for writing The Wonderful Wizard of Oz. He wrote 55 novels in total, plus four "lost" novels, 83 short stories, over 200 poems, and more.