Travis County was founded on January 25, 1840, by an act of the Fourth Congress of the Republic of Texas, only days after the town of Waterloo was renamed Austin and appointed as the state capital. William Barret Travis, the heroic leader of the Republic of Texas troops at the Battle of the Alamo, was honored with the name of the county.

The county was originally derived from Bastrop County, one of the initial twenty-three counties established in 1836. The Travis District, which covered around 40,000 square miles, was the name given to the surrounding area. Comal, Gillespie, and Hayes counties were formed from the Travis District in 1846, Burnet and Brown counties in 1852, Brown and Lampasas counties in 1856, and Runnels, Taylor, Eastland, Coleman, Runnels, and Callahan counties in 1858. Travis County now has a total area of 989 square miles.

The first county authorities were elected in February 1840, when the population was estimated to be 856.The local government got to work right once, forming four militia patrols and finding a suitable location to serve justice for the fledgling county.

The first schools in Travis County were private schools that convened in people's homes or were given space from a church or Masonic lodge. However, by the late 1840s, more extensive private facilities had begun to arise.

In 1855, the first legally recognized courthouse was built. Ever since, Travis County administration has been housed in two more Courthouses: the majestic 1876 facility and the present Courthouse, which was built in 1930.

When the Republic of Texas Congress chose Waterloo as the new capital's location, critics were quick to point out the drawbacks. Despite this opposition, the new capital was approved on January 19, 1840, and changed to Austin in honor of Stephen F. Austin. Congress created Travis County a few days later, named it after William Barret Travis, and designated Austin as the county seat.