Flat Mountain
The Flat Mountain is the flat-topped mountain on which the Flatheads live.
First named in Glinda of Oz, ch. 9
At that time the Flatheads were ruled by three Adepts in Sorcery, beautiful girls who were not Flatheads, but had wandered to the Flat Mountain and made their home there.
Where this is
placed In Oz worked out
read out of the chapters cited on this page, not stated in any one sentence of them
Lady Aurex calls the Skeezer/Flathead territory 'this forsaken corner of the Land of Oz' in Glinda of Oz ch.9.