Round Rock is on Interstate Highway 35 in south central Williamson County, sixteen miles north of downtown Austin. It was established on the north bank of Brushy Creek where Jacob M. Harrell, formerly a blacksmith in Austin, set up his shop during the spring of 1848. The settlement was first called Brushy Creek. Thomas C. Oatts, who became the first postmaster in 1851, was asked by postal officials to submit another name, and on August 24, 1854, the town officially became Round Rock, as suggested by Oatts and Harrell, who often fished together from a large anvil-shaped limestone rock in Brushy Creek near their dwellings. The Chisholm Trail, used by early cattle drivers on their way to Kansas, passed through Round Rock, crossing Brushy Creek near the rock.
Washington Anderson had settled a short distance east of the original Round Rock in 1843 and built a gristmill, which was washed out by a flood in 1845. A later mill was installed west of the round rock near the present low-water bridge and dam. During the Civil War a wool-carding factory opened nearby, and in the 1870s a gin was erected. Greenwood Masonic Institute, a three-story structure, opened in 1867 and was operated by the Masonic Lodge until 1881, after which the Cumberland Presbyterian Church agreed to take over its administration. They renamed it Round Rock Institute. It burned down on April 9, 1883, and a new two-story building was constructed on College Hill. This building burned down in 1913. Local citizens administered the institution until it was transferred to the public schools in 1888.
In 1876, when the International-Great Northern Railroad was built through Williamson County, its tracks were laid a short distance south and east of Round Rock. The community began to move toward the railroad and the south bank of Brushy Creek, building at first a tent city that was referred to for a time as "new" Round Rock. The original site was largely abandoned and was called Old Round Rock in official records. Since 1970 the town has developed in all directions, and so-called Old Town, consisting of a few restored limestone structures, is now surrounded by the rest of the city.
Within a year after the coming of the railroad, the town had a dozen businesses and professional offices, several hotels, a new broom factory, a lime plant operated by William Walsh, and two short-lived newspapers. The town's prosperity drew outlaw Sam Bass to the area in 1878; his capture and death after a shootout that year are commemorated annually during the town's Frontier Days celebration. In 1879 the Round Rock Searchlight was established. This newspaper became the Round Rock Leader in 1896 and was still operating in the 1990s. Trinity Lutheran College was established in the community in 1906; it merged with the Lutheran College of Seguin in 1929. The Round Rock Cheese Factory opened in 1928 and operated until the early 1970s.
During the first six decades of the twentieth century, Round Rock had a population between 1,000 and 1,400. The town began to grow in the 1960s and became the site of much historic restoration and preservation work. The 1970s brought dramatic growth, as nearby Austin expanded and brought large-scale development to Round Rock. The town became a bedroom community for Austin and a site for manufacturing and industry. Its population rose between 1970 and 1980 from 2,811 to 11,812. Growth continued in the 1980s as the city became home to several computer-related industries and over 300 retail businesses. In 1990 the population was 30,923.