  st. elmo is a city in fayette county, illinois, united states. the population was 1,426 at the 2010 census. st. elmo was established in 1871. ==geography== st. elmo is located at  (39.026709, -88.852062). according to the 2010 census, the city has a total area of , of which {{c
1871_establishments_in_Illinois Cities_in_Illinois Populated_places_established_in_1871