Jo's YWCA uniform (like much of her clothing in the latter half of the film) is characteristic of World War II, when the film was released, and not World War I, in which it is set. Her uniform's shoulders are too broad and the skirt too short, and she is wearing sheer stockings and pumps instead of opaque stockings and high boots or oxfords.
A Southern Pacific "cab-forward" locomotive is seen pulling the train at the start of the movie. It is shown stopping in Iowa to let the main characters disembark. The SP does not, and never has, run into Iowa.