Cross-posted from here.
By now, I suppose we all realize that life of sorts can exist in pretty much any medium in the fairyland shown in the Oz books, so it shouldn't be surprising that the skies above the land are also rather well-populated. Polychrome, one of the Daughters of the Rainbow and a Sky Fairy, is known for sometimes visiting the Earth. The Oz books also refer to Cloud Fairies, made of a fleecy substance. And in John R. Neill's books, we see sky sweepers and scrapers who clean up debris in the air, as well as the windbag-like Cloud Pushers who help guide the clouds. The Ozian skies are also dotted with several floating islands, the first and most famous of them being Sky Island.
The book Sky Island, in which the titular land first appears, is not an Oz book, but was intended to be tied in with the series. Button-Bright and Polychrome, who had earlier had significant roles in The Road to Oz, show up again in Sky Island. The island itself, which the protagonists accidentally reach by means of Button-Bright's Magic Umbrella, is divided into two main countries. Each one is color-coded like the quadrants of Oz, but the color schemes are even more pervasive. The dark Blue Country, where the sun never shines and snubnoses are considered a sign of beauty, is ruled by the Boolooroo. While allegedly an elected office, each Boolooroo actually chooses his own successor, and forces everyone else to vote for that person. The Pink Country is much brighter and seemingly friendlier, yet the inhabitants can be quite hostile at times. The people are divided in a feud over whether the sunrise or sunset is more beautiful, and punishment for some crimes involves pushing people off the edge of the island. The ruler of the Pink Country is whichever person has the lightest shade of pink skin, and at one point there was a law that the ruler's power had to be countered by the monarch living in poverty, but this was later altered. In fact, the entire island underwent some major changes when Trot, through a combination of legal interpretation and conquest, became ruler of both countries. The two colored territories are separated by the Fog Bank, a damp area inhabited by enormous frogs and other abnormally large animals. There's a fun surreal moment when the heroes come across a giant lizard who's dreaming of parsnips.
The next major appearance of a skyland is in The Cowardly Lion of Oz, in which the main characters are carried off to the Skyle of Un (a skyle being an isle in the sky). The inhabitants, known as Uns, are strange and disagreeable bird-people. Eventually, the heroes learn that anyone on the island grows a feather whenever he or she does anything un-ish. The Uns live in treehouses, and go fishing for birds. Previously, they spent most of their lives shouting out their wishes and fighting each other, but they apparently reformed when Ozma placed Unselfish, known as the only good Un, on the throne.
A few other Thompson Oz books feature lands in the sky. Grampa has the characters visiting a country in the clouds, where they encounter Polychrome, a star shepherdess named Maribella, and several disembodied heads. Much of the plot of Speedy takes place on Umbrella Island, a land in the Nonestic Ocean that the wizard Waddy rigged with a magical mechanical umbrella in order to make it fly. In Enchanted Island, King Rupert of Kapurta uses a magic vest button to turn his country into an island in the sea, then later one in the sky. And Ozoplaning with the Wizard is largely set in the sky, and specifically in the Kingdom of Stratovania, which is where I got the name for this journal. As the name suggests, Stratovania is located in the stratosphere, about twenty miles above the Land of Oz. Inspired by the success of Captain Salt in claiming countries for Ozma, the Tin Woodman tries to do the same with Stratovania, but that doesn't go over too well with its ruler Strutoovious VII. In fact, he's so incensed that he decides to invade Oz; and while the Wizard and Ozma manage to repel the attack without too much trouble, it's quite possible that the Ozites thought twice about expanding their empire after this. The land and buildings in Strut's kingdom are made of solid air, which I would think would generally require temperatures pretty close to absolute zero, but I suppose these things can work differently in fairyland. After all, Nimmie Amee also uses a compound that she took from the Wicked Witch of the East to form a wall of solid air around her house, as seen in Tin Woodman.