Permanent settlement began in this area in the late 1830s. By 1848, former Austin Mayor Jacob Harrell moved here, selling town lots near the Stagecoach Road crossing at Brushy Creek. A post office named "Brushy Creek" opened in 1851 in Thomas Oatts' store. Three years later, the name changed to "Round Rock" for a distinctive limestone formation marking a natural ford for wagons. With immigration from several states and Sweden, the population doubled during the 1850s, bringing new stores, churches, fraternal lodges and grain mills. The first institution of higher learning, Round Rock Academy, began in 1862. After the Civil War, the former trail and stage road became a prominent cattle drive route.
In 1876, the International-Great Northern Railroad developed a new townsite east of the existing Round Rock. A commercial district sprang up along Georgetown Avenue (Main Street) with construction of many limestone buildings. "New Town" quickly eclipsed the established settlement, whose postal name changed again to "Old Round Rock." For months, the new site was the railroad terminus, bringing lumber and flour mills, cotton gins, blacksmith and wagon shops, banks, hotels, restaurants, stores and schools. Round Rock challenged the state capital for economic control of central Texas, boasting
six hotels to Austin's five and serving as the retail hub for several counties to the west. The railroad also made Round Rock a more cosmopolitan place, bringing new residents from all over the U.S. And all around the world. Well-positioned for growth by its location on major transportation routes, Round Rock became one of the nation's fastest-growing cities by the late 20th century. Two dozen commercial buildings in Round Rock's historic downtown were listed in the National Register of Historic Places in 1983.