Georgetown is a city in and the county seat of suburban Williamson County, Texas, United States, with a population of 47,400 at the 2010 census. Southwestern University, founded in 1840, the oldest university in Texas, is located in Georgetown, about one-half mile from the historic square. Sun City Texas (formerly called Sun City Georgetown) is a large retirement-oriented and age-restricted development which constitutes more than one-third of the Georgetown population. Georgetown has a notable range of Victorian commercial and residential architecture. In 1976, a local historic ordinance was passed to recognize and protect the significance of the historic central business district and in 1977 the Williamson County Courthouse Historic District, containing some 46 contributing structures, was listed on the National Register of Historic Places. Georgetown is called the "Red Poppy" Capital of Texas for the many red poppy(Papaver rhoeas) wildflowers planted throughout the city and in many residents' front yards, which bloom each Spring. Georgetown also holds a Red Poppy Festival in April each year. The festival attracts up to 30,000 visitors annually. Geographically, Georgetown lies across the Balcones Escarpment, a fault line that divides Georgetown into areas roughly east of Interstate 35 in the Blackland Prairie which is flat farmland characterized by having black, fertile soils, where cotton is the primary crop; and the west side of the Escarpment which consists of hilly, karst-like terrain pocketed with vugular limestone openings that allow water to percolate through the limestone and into the Edwards Aquifer below. The area typically has little topsoil and has higher elevations, and is considered part of the Texas Hill Country.