Aunt Jane's Nieces on the Ranch is a juvenile novel for girls, written by L. Frank Baum. It is the eighth book in the Aunt Jane's Nieces series, and carries forward the continuing story of the cousins Louise Merrick, Patsy Doyle, and Elizabeth De Graf. Like all the books in the series, it was released under Baum's "Edith Van Dyne" pen name.
Louise is now living on a ranch near Escondido, California with her husband Arthur Weldon and their new baby, the five-month-old Jane Merrick Weldon. (In Baum's flexible chronology, Louise is still only twenty years old.) Cousins Patsy and Beth, along with Uncle John and Major Doyle, come west for a visit. Concerned about the baby, they bring with them a professional nurse named Mildred Travers; Beth knows the young woman from her charity work.
The visitors are welcomed to the Weldon's "ranch," which consists of 300 acres of orange and olive groves surrounding a traditional Spanish-style house. The house is constructed of adobe; its oldest sections have walls eight feet thick.
A conflict quickly develops between the new nurse Mildred Travers and Inez, the young Mexican woman who has been caring for the infant Jane. The passionate Inez hates her rival, whom she considers a witch — Mildred knows more about the house and the neighborhood than a stranger should. Patsy learns that Mildred was born and raised in the area, and in fact has been in the Weldon house many times as a child, when it was owned by Cristoval, the last of the family of Spanish settlers who built it.
The visitors meet some of the other ranchers in the neighborhood; these tend to be people like the Weldons, financially-well-off newcomers from the East. One day, the Weldons and their visitors join other neighbors for a lunch in town; when they return home, they are shocked to find that baby Jane and both her nurses have disappeared. A frantic search of the neighborhood is conducted, without results. Major Doyle is awakened in the night by what at first sounds like the house's legendary ghost; the searchers realize that the sounds are coming from within the walls.
The plot flashes back to explain how the two nurses and the baby got trapped in secret chambers within the house's massive walls. In the process, the story reveals that Mildred is the daughter of a local man named Michael Leighton, who partnered with Cristoval in smuggling activities; Mildred had hoped to find the hidden money that Cristoval held for her father when Leighton was finally arrested and sent to prison.
During their enforced confinement, the two nurses get to know each other, and Inez overcomes her hostility to Mildred. Through a long struggle, the searchers eventually manage to free the trapped nurses and baby, none the worse for wear.
The secret rooms are examined carefully, though no treasure is found. A new secret is revealed by Miguel Zaloa, the old ranchero who manages the staff for Weldon. Miguel exposes another secret compartment in the walls, where Leighton's money — four bags of gold — was kept by Cristoval, waiting the man's return. With this fortune, Mildred's financial needs are satisfied; she accepts a marriage proposal from one of the neighboring ranchers.
As the Aunt Jane's Nieces continues, element of redundancy begin to appear. This is the second novel, after Aunt Jane's Nieces and Uncle John, that involves a trip to southern California. The previous novel, Aunt Jane's Nieces on Vacation, was the second that dealt with a summer in the Adirondacks (after Aunt Jane's Nieces at Millville).
Baum addresses the problem of redundancy with the introduction of more supporting characters; on the Ranch is the first book in the series in which supporting characters come to dominate the plot, while the continuing characters play more supporting roles.
This novel shares a central weakness with the prior California book in the series: the plots of both are heavily dependent upon coincidence.
On the Ranch features two important supporting characters, the nurse Inez and the ranchero Miguel Zaloa, who are Hispanic, or "Mexican" in the terms of the novel. The book's treatment of its Hispanics falls short of modern standards of political correctness: the Mexicans are regarded as lazy and ignorant by the protagonist white characters. In effect, though, Baum gives affirmative portrayals of the two characters, picturing them as honest, diligent, and caring.