For the film, see The Wizard of Oz.
For the book sequels, and the series as a whole, see Land of Oz.The Wonderful Wizard of Oz
was written as an allegory of the politics at the time. The old gray world of Kansas had the farmers beaten down and cynical. Then in the world of Oz, the Scarecrow also represented the farmer, perhaps exploited by finance that they were reduced to mere straw men. The Tin Woodman was the urban worker, beaten down and dismembered as to lose all his humanity and be a mere machine. The Cowardly Lion represented William Jennings Bryan, a politician who could save us if he but developed the courage.
The Yellow Brick Road represented the gold standard, promising the bright society, but ultimately underneath, all fake and false promises.
There was probably much more, and I might have gotten part of it wrong as it is.