The central region of Texas covers the state's three largest cities: Houston, Dallas-Fort Worth and San Antonio. The limestone terrain of Texas Hill Country lies in Central Texas, as do the state's three largest rivers, the Trinity, the Brazos and the Colorado. A total of around 7,000 acres were listed for sale in Travis County recently, representing a total value of $1 billion in Travis County land and rural real estate for sale. Travis County ranks 21st out of 254 counties in the Lone Star State for the total acreage of land currently advertised for sale. There were three properties listed as sold in Travis County through the Land Network Comparable Sales Program. This represented a total value of $2,445,000. Of all ranches, farms, hunting land and other rural land and acreage for sale in Travis County, Austin featured the most land for sale. From an economic perspective, government and state-level services contribute most to Travis County's overall GDP. Travis County is the 75th biggest county (1,023 square miles) in Texas. It's located in the Blacklands South Texas region of the state.