Rockdale owes its founding to the International & Great Northern rail line, along which the town was laid out in 1873-74. The railroad gave area farmers access to markets for their crops, and Rockdale became a shipping point for farmers and other local businesses. The San Antonio & Aransas Pass (later Southern Pacific) Railroad operated a north-south route through Rockdale from 1891 to 1959, further contributing to economic growth. The Rockdale, Sandow and Southern Railroad, chartered in 1923 to carry lignite coal to area customers, became Rockdale's third rail line. Although the last passenger train left Rockdale in 1970, the railroad remains a significant part of the community's heritage. (2001)