Let me preface this by saying that even though I'm using panels from Eric Shanower and Skottie Young's adaptation to illustrate this, my gripe is in no way about them. Their adaptations are extraordinarily faithful to the source material, so the problem is all L. Frank Baum.
Here's the deal:
In the first book, The Wonderful Wizard of Oz, the Wizard explains that when he arrived in Oz, he took advantage of the locals and made them build the Emerald City for him. That made an impression on me, because it's pretty huge evidence that - contrary to his own assertions - he's no more a "good man" than a "good wizard." This history of the Emerald City is repeated early in the second book, The Marvelous Land of Oz.
But then later in Marvelous Land, the Scarecrow - current ruler of the Emerald City - offers a completely different history.
It's that version that Baum sticks with for the rest of the book. In fact, he hinges the entire plot on it since the whole story is about who actually has the right to rule the Emerald City. If you haven't read it, all I'll say is that there's a revolt that calls the legitimate rulership into question and Pastoria is an important part of the discussion.
Sure that I'm not the first to notice this, I went to Wikipedia and found that the problem's made more complicated in Dorothy and the Wizard in Oz, where it's revealed that it was the Wizard who ordered the city built, but that he didn't usurp it directly from Pastoria. The witches took it from Pastoria and the Wizard took it from them.
What all this means is that Baum was serious when he wrote in the preface to Wonderful Wizard that it was "written solely to please children" of his day. In other words, "You nerds need to lighten up and leave it alone." And I will try.
I do like how the Marvel adaptation of Marvelous Land fixes another possible continuity error that Wikipedia mentions though. In Wonderful Wizard, it's explained that the Emerald City isn't actually green-colored, but only appears to be because of the green-lensed goggles the tyrannical Wizard forced his subjects to wear from birth to death. I thought it pretty cool that halfway through Marvelous Land, the new leadership of the city drops the goggles and the city is colored normally for the rest of the book. Wikipedia points out that "the city is still described as green" in Baum's novels, but Marvel's colorist, Jean-Francois Beaulieu gives it plenty of natural greenery without the pervasive tint that everything has in Wonderful Wizard and the early parts of Marvelous Land.
With the goggles:
Without the goggles:
There's even a change in the city's attitude about its former leader, revealing that they're now more aware of the Wizard's deception. I won't post the spoilery panel, but there's a scene late in the book where a resident of the city declares that the Wizard "claimed to do things he couldn't." Though it happens off the page, apparently the citizens have realized that the Wizard was a sham and that's a nice bit of continuity development. I hope there's more stuff like that than like the shaky history of the place.