Permanent settlement in this area began in the late 1830s. By 1848, former Austin Mayor Jacob Harrell had moved here and was selling town lots near the Stagecoach Road crossing at Brushy Creek. A post office named Brushy Creek opened in 1851 in Thomas Oatts' store, and three years later the name changed to Round Rock for a distinctive limestone formation that marked a natural ford for wagons. Immigration from several states and Sweden doubled the population during the 1850s and brought new stores, churches, fraternal lodges, and grain mills. Round Rock Academy, the first institution of higher learning, 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 community, and a commercial district rose along Georgetown Avenue, or Main Street, with many limestone buildings. New Town quickly eclipsed the established settlement, whose postal name changed again to Old Round Rock. For months, the new site served as 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, with six hotels to Austin's five, and served as the retail hub for several counties to the west. The railroad also made Round Rock more cosmopolitan by bringing new residents from across the U.S. and around the world. Well positioned by its location on major transportation routes, Round Rock became one of the nation's fastest-growing cities by the late 20th century. In 1983, two dozen commercial buildings in its historic downtown were listed in the National Register of Historic Places.