There are 16 US Post Offices in Greenbrier County serving a total of 33,861 residents equating to 2,116 residents per post office. It's estimated that approximately 54,046 packages are handled across the 16 county post offices annually. Greenbrier County /\u02c8\u0261ri\u02d0nbra\u026a\u0259r/, is a county located in the U.S. state of West Virginia. As of the 2010 census, the population was 35,480. Its county seat is Lewisburg. The county was formed in 1778 from Botetourt and Montgomery counties in Virginia."