North Vernon is a city in Jennings County, Indiana, United States. The population was 6,608 as of the 2020 census. North Vernon was origiā¦North Vernon is a city in Jennings County, Indiana, United States. The population was 6,608 as of the 2020 census. North Vernon was originally called Tripton, and is sometimes referred to as āThe Gem of the Midwestā, under that name, it was platted in 1854.