The Twenty-One Balloons by William Pène du Bois is a 1947 children's fantasy-adventure novel set in 1883. It follows Professor William Waterman Sherman, a retired schoolteacher who embarks on a year-long solo journey across the Pacific Ocean in a custom-built hot air balloon. A week into his trip, a seagull punctures the balloon, forcing him to crash-land on the volcanic island of Krakatoa. There, he discovers a secret, wealthy society of twenty families living off a vast diamond mine. Each family, named alphabetically (A to T), operates a unique restaurant serving international cuisine on designated days, creating a "Gourmet Government" where they work one day and rest for nineteen. The island is filled with whimsical inventions, like a Balloon Merry-Go-Round and elaborate houses with features such as bumper-car-like furniture. When Krakatoa’s volcano erupts, the residents and Sherman escape on a platform lifted by twenty balloons. They drift across the world, with families parachuting to safety in places like India and Belgium, while Sherman and the F family land in the Atlantic, where he is rescued. Back in San Francisco, Sherman shares his tale at the Explorers’ Club, revealing diamond cufflinks to fund a new balloon adventure. The novel, a 1948 Newbery Medal winner, blends imagination, science, and humor, though some critics note its dated portrayal of the utopian society.