Decline in population during the twentieth century was caused by the disappearance of tenant farming and sharecropping. During the depression there was a back-to-farm movement. There was an increase in farm wages. As a result there were wide employment possibilities in industry and increased use of farm machinery which required fewer unskilled laborers.

The principal result of the construction of the Alcoa plant has been the growth of population in Rockdale. The city's population tripled in a few months. New residential additions had been laid out, and in them new dwellings were built. Traffic increased, parking meters were erected. A transit bus and taxis appeared. To take care of the population increase, the city issued $125,000 for water and sewage and a million dollars for schools.