There are 56 US Post Offices in Dallas County serving a total of 1,938,176 residents equating to 34,610 residents per post office. It's estimated that approximately 3,093,545 packages are handled across the 56 county post offices annually. Dallas County is a county located in the U.S. state of Texas. As of the 2010 census, the population was 2,368,139. It is the second-most populous county in Texas and the ninth-most populous in the United States. Its county seat is Dallas, which is also the third-largest city in Texas and the ninth-largest city in the United States. The county was founded in 1846 and was possibly named for George Mifflin Dallas, the 11th Vice President of the United States under U.S. President James K. Polk. Dallas County is included in the Dallas\u2013Fort Worth\u2013Arlington, TX Metropolitan Statistical Area (colloquially referred to as the Dallas/Fort Worth Metroplex)."