Lavaca County is a county located in the U.S. state of Texas. As of the 2020 census, its population was 20,337. Its county seat is Hallettsville. The county was created in 1846. It is named for the Lavaca River, which curves its way southeast through Moulton and Hallettsville before reaching the coast at Matagorda Bay.

Jackson County is a county in the U.S. state of Texas. As of the 2020 census its population was 14,988. Its county seat is Edna. The county was created in 1835 as a municipality in Mexico and in 1836 was organized as a county. It is named for Andrew Jackson, President of the United States from 1829 to 1837.