There are 7 US Post Offices in Millard County serving a total of 11,245 residents equating to 1,606 residents per post office. It's estimated that approximately 17,948 packages are handled across the 7 county post offices annually. Millard County is a county located in the U.S. state of Utah. As of the 2010 census, the population was 12,503. Its county seat is Fillmore, and the largest city is Delta. The county was created in 1851. The county and its seat were named for Millard Fillmore, thirteenth President of the United States."