Port Lavaca is a city in Calhoun County, located in the U.S. state of Texas. The population was 12,248 at the 2010 census and 11,557 at the 20…Port Lavaca is a city in Calhoun County, located in the U.S. state of Texas. The population was 12,248 at the 2010 census and 11,557 at the 2020 census. It is the county seat of Calhoun County and part of the Port Lavaca, Texas micropolitan statistical area. Port Lavaca is 130 miles southwest of Houston.