- Your Ad Here Town of Big Flats Chemung County is a county located in the U.S. state of New York. As of the 2016 census, the population was 86,322. Its county seat is Elmira. Sponsored Links History Chemung County was formed in 1836. Its name is derived from the name of a Delaware Indian village (meaning "big horn"). Many signs posted along roads in Chemung County refer to the area as "Mark Twain Country" because of the many years the author lived and wrote in Elmira. |