Georgetown, Texas. Georgetown is a city in and the county seat of Williamson County, Texas, United States, with a population of 47,400 at the 2010 census and a population of 63,716 at the 2016 Census estimate. It is 30 miles from Austin. Southwestern University, the oldest university in Texas, founded in 1840, is located in Georgetown about one-half mile from the historic square. Sun City Texas is a large retirement-oriented and age-restricted development that constitutes more than one-third of Georgetown's population.