There are 6 US Post Offices in Jefferson County serving a total of 6,930 residents equating to 1,155 residents per post office. It's estimated that approximately 11,061 packages are handled across the 6 county post offices annually. Jefferson County is a county located in the U.S. state of Oklahoma. As of the 2010 census, the population was 6,472. Its county seat is Waurika. The county was created at statehood and named in honor of President Thomas Jefferson."