There are 4 US Post Offices in Upshur County serving a total of 25,729 residents equating to 6,432 residents per post office. It's estimated that approximately 41,066 packages are handled across the 4 county post offices annually. Upshur County is a county located in the eastern part of the U.S. state of Texas. As of the 2010 census, the population was 39,309. The county seat is Gilmer. The county is named for Abel P. Upshur who was U.S. Secretary of State during President John Tyler's administration. Upshur County is part of the Longview, Texas Metropolitan Statistical Area as well as the Longview\u2013Marshall, TX Combined Statistical Area."