Iron City, Tennessee. Iron City is a census-designated place (CDP) in Lawrence and Wayne counties, Tennessee. The population was 328 at the 2010 census when it was a city, and estimated at 180 in 2013 as a CDP. Iron City was incorporated as a city from 1887 to 1901, and again from 1962 until 2010, its residents voting to disincorporate in the latter year.