Fictional universes are nothing new in children’s literature and it’s been acknowledged for some time that contemporary techniques for worldbuilding so widely used in science fiction, fantasy, video games were explored by authors like Lewis Carroll, George MacDonald, and Charles Kingsley in the mid-nineteenth century. 
Makers of alphabet, toy, and cloth books also began to visualize shared worlds within the children’s literature universe around the same time. By 1871, an uncredited artist created a set of puzzle pictures in The Alphabet of Fairy Tales in the Routledge Shilling Toy Book series. In the shadow of the house that Jack built, the forty thieves glower at Goody Two Shoes, while Little Thumb scampers by in his seven league boots, and Mother Goose hovers overhead. The rhyming captions provides clues as to the identity of the various characters in this enchanted space where no one from the real world has blundered into.
Mother Goose takes on a new role in the early twentieth century presiding over a land populated by the familiar characters in nursery songs and lullabies, which over time has taken many increasing ingenious forms. Polly-Peters Picture-Map and Guide to Mother Goose Land (ca. 1921), draws the realm in the shape of the good old dame in her steeple hat flying on a goose, with their features superimposed on the northernmost reaches of the continent and the bird’s webbed feet trailing over the sea.
Gathered within her outline are her silly subjects, all recognizable from the original ditties, but otherwise unconnected by any geographical logic. Alan and Janet Ahlberg did not need maps on the endpapers to their two iterations of 
Mother Goose Land in Each Peach Pear Plum or the Jolly Postman series because the action centered on a ramble through the countryside in the first, and a mailman on his bicycle delivering the post to the residents in the second. While readers cannot give directions from one house to the next on the mailman’s route, they know that names of the different houses and their addresses because they are printed on the envelopes in the book.
One of the few startling narratives set in this country is William Pene du Bois’ Mother Goose for Christmas (c.1972), a miniature cozy mystery. The old lady is a poet and proprietor of a book shop with an attached day care in a tiny village that has no policeman. On Christmas Eve, the villagers are horrified to see two strange suspicious looking men dragging the dame and Goosey Gander towards the boarded-up bakery.
Soon after they break and enter, clouds of black smoke rise from the chimney and the concerned villagers, terrified that Mother Goose is being mistreated and Goosey Gander roasted, build a bonfire to keep them warm so they can sing Christmas carols all night and forestall disaster. By morning, the smoke is bearing the delicious smells of sugar and spice, but fears are still running high. Suddenly the shutters of the bakery burst open, the thugs appear in pure white aprons and wide smiles just as Mother Goose flies in to introduce them to Simple Simon and the Knave of Hearts, the new owners of the Queen’s Bakery.
More recently Chris Raschka and Vladimir Radunsky compiled Mother Goose of Pudding Lane: A Small Tall Tale (2019) a typically quirky collaboration which is a nursery rhyme anthology that is also tells the story of Mother Goose and her husband Isaac, based on the hoary old urban legend that the patron saint of nursery rhymes and fairy tales was a real person, an Elizabeth Goose living in Boston at the end of the seventeenth century. The author and illustrator cleverly frame rhymes as responses, comments, or extensions to the stages of the Gooses’ lives. The newly weds start a family immediately and it grows so large so quickly that Elizabeth herself is cast as the old woman in the shoe. The object that looks like a coal scuttle at the bottom is really the heel of the family home.
As long as Mother Goose Land belongs to no one and everyone, there can never be a definitive iteration, but rather many delightfully different ones from which we can enjoy.
