There are 20 US Post Offices in Denton County serving a total of 497,769 residents equating to 24,888 residents per post office. It's estimated that approximately 794,495 packages are handled across the 20 county post offices annually. Denton County is a county in the U.S. state of Texas. As of the 2010 census, its population was 662,614, making it the ninth-most populous county in Texas. The county seat is Denton. The county, which was named for John B. Denton, was established in 1846. Denton County is included in the Dallas-Fort Worth-Arlington, TX Metropolitan Statistical Area. In 2007, it was one of the fastest-growing counties in the United States."