There are 14 US Post Offices in Dallas County serving a total of 52,982 residents equating to 3,784 residents per post office. It's estimated that approximately 84,565 packages are handled across the 14 county post offices annually. Dallas County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 66,135. Its county seat is Adel. The county was named for George M. Dallas, Vice President of the United States of America under James K. Polk. Dallas County is included in the Des Moines\u2013West Des Moines, IA Metropolitan Statistical Area."