Liberty is a city in and the county seat of Liberty County, Texas, United States and a part of the Houston-Sugar Land-Baytown metropolitan area. The population was 8,033 at the 2000 census. Liberty is the third oldest city in the stateestablished in 1831 on the banks of the Trinity River. The city also has an exact replica of the Liberty Bell from Philadelphia, Pennsylvania. Its area code is 936 and its ZIP code is 77575. Liberty, Texas is the county seat of Liberty County and the third oldest town in Texas. Texas heroes William B. Travis, Sam Houston, and David Burnet all practiced law in Liberty.