Plainville is a city located in Gordon County, Georgia. The population of Plainville was 313 at the 2010 census, up from 257 at the 2000 cens…Plainville is a city located in Gordon County, Georgia. The population of Plainville was 313 at the 2010 census, up from 257 at the 2000 census. Plainville was incorporated in 1903. The name is a transfer from Plainville, Connecticut.