Austin is the capital city of the U.S. state of Texas and the seat of Travis County, with portions extending into Hays and Williamson counties. It is the 11th-most populous city in the United States, the fourth-most-populous city in Texas, and the second-most-populous state capital city. It is also the fastest growing large city in the United States and the southernmost state capital in the contiguous United States. As of the U.S. Census Bureau's July 1, 2018 estimate, Austin had a population of 964,254 up from 790,491 at the 2010 census. The city is the cultural and economic center of the Austin–Round Rock metropolitan statistical area, which had an estimated population of 2,168,316 as of July 1, 2018. Located in Central Texas within the greater Texas Hill Country, it is home to numerous lakes, rivers, and waterways, including Lady Bird Lake and Lake Travis on the Colorado River, Barton Springs, McKinney Falls, and Lake Walter E. Long.