Rockdale is located northeast of Austin between Waco and Giddings along US 79 and US 77 in Milam County.
The new town was named by Mrs. B.F. Ackerman for a nearby rock, which was twelve feet high and had a circumference of twenty feet.
In the early 1950s the Aluminum Company of America discovered an inexpensive method of converting lignite into electricity and decided to locate a new aluminum plant near Rockdale and the lignite mine at Sandow.
The lignite industry continued to prosper, signing leases with Shell Oil and Texas Power and Light in the 1970s.
Rockdale had a population of 4,481 in the early 1960s, but increased steadily from the mid-1960s through the 1980s; 5,810 residents and 130 businesses were reported in 1988. The population in 1990 was 5,235.