There are 6 US Post Offices in Dade County serving a total of 7,767 residents equating to 1,295 residents per post office. It's estimated that approximately 12,397 packages are handled across the 6 county post offices annually. Dade County is a county located in the southwest part of the U.S. state of Missouri. As of the 2010 census, the population was 7,883. Its county seat is Greenfield. The county was organized in 1841 and named after Major Francis L. Dade of Virginia, who was killed in the Seminole War in 1835.