Polk County is a county located in the U.S. state of Texas. As of the 2010 census, the population was 45,413. Its county seat is Livingston. The county is named for James Knox Polk, the eleventh president of the United States, who was President when Texas became a state through annexation.The Alabama-Coushatta Indian Reservation of the federally recognized tribe is in Eastern Polk County, where the people have been since the early 19th century, after migrating from the Southeast.