We know that the land of Oz resides in one's imagination (or dreams, in the movie version), but we also know that Dorothy grew up in Kansas. The Wizard of Oz wiki looks at Baum's clues as to the location of the farm. In The Road to Oz, the nearby town of Butterfield is mentioned, which is not in Kansas, but in Missouri near the Arkansas border, a couple of counties away from the southeastern corner of Kansas. Baum might have just liked the name. Not knowing the exact location of the farm in The Wonderful Wizard of Oz did not stop anyone from claiming it. Read about several places that lay claim to Dorothy or Oz in this article I wrote for mental_floss.