Travis County is a county in the U.S. state of Texas. As of the 2010 census, the population was 1,024,266; the estimated population in 2019 was 1,273,954. It is the fifth-most populous county in Texas. Its county seat is Austin, the capital of Texas. The county was established in 1840 and is named in honor of William Barret Travis, the commander of the Republic of Texas forces at the Battle of the Alamo.