In Return to Oz, the Emerald City is in ruins, its residents turned to stone by the Nome King, and ruled by Mombi and her Wheelers, but Dorothy Gale later uses the Ruby Slippers to restore everybody and everything to life.
In Oz the Great and Powerful, Evanora the Wicked Witch of the East and the Wicked Witch of the West had taken over the Emerald City and used it as their personal headquarters. The residents lived unaware of their rulers' tyranny until they discovered the truth and attempted to rebel against them. After Oscar Diggs becomes the Wizard of Oz and drives the two witches out of Emerald City, Glinda the Good Witch of the South reclaims her rightful place as ruler of the Emerald City, with Oscar ruling by her side.