Dallas County is the second-most populous county in the U.S. state of Texas. As of the 2020 U.S. census, the population was 2,613,539, making it the ninth-most populous county in the country. Dallas County is included in the Dallas-Arlington-Fort Worth metropolitan statistical area—colloquially referred to as the Dallas–Fort Worth metroplex. Municipal expansion within Dallas County has blurred the geographic lines between cities and between neighboring counties.