The Eastern quadrant of Oz is known as Munchkin Country. This is a rather famous section of Oz , as it's where Dorothy's house landed when she first arrived in Oz. Other than that, it's really rather boring. Munchkin Country is where many Oz adventures start, but heroes rarely stay there for long.
And now for the big question: Just how tall is a Munchkin?
In The Wonderful Wizard of Oz, the Munchkins Dorothy meets are roughly her own height. Since Dorothy is depicted as being a little girl, most people presume that Munchkins must be very small. Especially since this is how they are depicted in the film version.
My own theory is that Munchkins are only slightly shorter than normal people. While her age is not stated in Wizard, she is noted as being tall for it. I take this to mean that she is old enough to be going through puberty and in the midst of her first growth spurt. So the Munchkins may indeed be smaller than most people, but not by too very much.
There was also a narrative reason behind the size of the Munchkins in that first story. If the Munchkins thought Dorothy was a little girl, they wouldn't have allowed her to undertake any adventures. But since they're the same size as her, they presume she's fully adult and able to take care of herself.
Amusingly, the word "Munchkin" has taken on an alternate meaning in the gaming community. I took some time a while back to talk more about that bit.
Watch out for the next few entries, where I use words that have distinct meanings for my Oz readers and for my gaming readers.