The Flatheads lived in a depression atop a mountain, located near the lake of the Skeezers.
Their name identified their most conspicuous feature: they were flat-headed, lacking craniums and foreheads. They kept their brains in canisters they carried about with them. (The canisters were vulnerable to theft.)
For a long time the Flatheads lived peacefully under the guidance of the Three Adepts. During their conflict with the Skeezers, they were under the thumb of their Supreme Dictator, or "Su-Dic." Once the "war" was over, the Three Adepts regained their former influence. The Flatheads were magically healed, given normal human heads with their brains on the inside. Flatheads no longer, they are now called Mountaineers. (Glinda of Oz)