Johnson City was a Federation settlement on the planet Gamma Hydra IV, established sometime after 2267. It was presumably named for Robert and Elaine Johnson, two casualties from the original science colony on the planet. In 2372, Odo disguised himself as a cargo container bound for Johnson City in order to board a Yridian freighter. (DS9 novel: The 34th Rule) Gamma Hydra and the Johnsons were established in TOS episode: "The Deadly Years".