Johnston is called The Hub of the Ridge because it is located at the meeting place of the three river systems which flow away from the Ridge, a fertile plateau about long between clay hills to the north and sand hills to the south. The area has been settled since the mid-1700s. In 1791 as George Washington traveled through the area on his triumphal tour through the country, he stopped at the Lott family plantation, just east of Johnston. In the late 1860s, the Charlotte, Columbia and Augusta Railroad expanded westward from Columbia to Augusta. Edward Jones Mims, M.D., persuaded William Johnston, president of the railroad, to run the railroad through the Mims plantation. In return, Dr. Mims agreed to name the new town for Mr. Johnston. In the early 1900s, the peach industry became successful in this area. Today, the Ridge produces about 60 percent of South Carolina's peaches. Johnston is proclaimed to be the "Peach Capitol of the World."
As of the census of 2000, there were 2,473 people, 923 households, and 635 families residing in the town. The population density was 930.6 people per square mile. There were 1,012 housing units at an average density of 403.2 per square mile. The racial makeup of the town was 35.92% White, 62.63% African American, 0.26% Native American, 0.13% Asian, 0.39% from other races, and 0.68% from two or more races. Hispanic or Latino of any race were 1.33% of the population. There were 923 households, out of which 30.0% had children under the age of 18 living with them, 41.6% were married couplesliving together, 22.6% had a female householder with no husband present, and 31.2% were non-families. 28.5% of all households were made up of individuals, and 12.4% had someone living alone who was 65 years of age or older. The average household size was 2.53 and the average family size was 3.12. In the town, the population was spread out, with 27.1% under the age of 18, 9.4% from 18 to 24, 26.7% from 25 to 44, 21.6% from 45 to 64, and 15.2% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 88.2 males. For every 100 females age 18 and over, there were 82.1 males. The median income for a household in the town was $25,570, and the median income for a family was $29,531. Males had a median income of $25,521 versus $19,572 for females. The per capita income for the town was $12,671. About 21.2% of families and 23.9% of the population were below the poverty line, including 28.9% of those under age 18 and 20.8% of those age 65 or over.
2010 Census
According to the 2010 census, the town had a population of 2,362. Of which, 1,481 were Black or African American, 845 were White, 18 were two or more races, 11 were some other race, 4 were Asian, 3 were American Indian or Alaska Native. 43 were Hispanic or Latino of any race.