There are 7 US Post Offices in Caldwell County serving a total of 37,497 residents equating to 5,357 residents per post office. It's estimated that approximately 59,849 packages are handled across the 7 county post offices annually. Caldwell County is a county located in the U.S. state of Texas. As of the 2010 census, the population was 38,066. Its county seat is Lockhart. The county was founded in 1848 and was named after Mathew Caldwell, a ranger captain who fought in the Battle of Plum Creek against the Comanches and against Santa Anna's armies during the Texas Revolution. Caldwell was also a signer of the Texas Declaration of Independence. Caldwell County is part of the Greater Austin metropolitan area."