Round Rock is a city located in Travis and Williamson counties in the US state of Texas. It is part of the metropolitan area. The 2009 census estimate places the population at 105,412. The city straddles both sides of the Balcones Escarpment, a fault line in which the areas roughly east of IH-35 are flat and characterized by having black, fertile soils of the Blackland Prairie, and the west side of the Escarpment which consists mostly of hilly, karst-like terrain with little topsoil and higher elevations and which is part of the Texas Hill Country. Located about 20 miles north of downtown Austin, Round Rock shares a common border with Austin at SH 45.

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