Rockmart is a city in Polk County, Georgia. The population was 4,199 according to a 2010 census. Rockmart developed as a railroad depot town when the Southern Railway built a station in the area. The community was incorporated in 1872, and was named from abundant deposits of slate in the area. The Rockmart Downtown Historic District is listed on the National Register of Historic Places.According to the United States Census Bureau, the city has a total area of 4.4 square miles (11 km2), of which 4.3 square miles (11 km2) is land and 0.04 square miles (0.10 km2) (0.69%) is water.