There are 7 US Post Offices in Gregg County serving a total of 111,559 residents equating to 15,937 residents per post office. It's estimated that approximately 178,061 packages are handled across the 7 county post offices annually. Gregg County is a county located in the eastern part of the U.S. state of Texas. As of the 2010 census, its population was 121,730. Its county seat is Longview. The county is named for John Gregg, a Confederate general killed in action during the American Civil War. Gregg County is part of the Longview, TX Metropolitan Statistical Area as well as the Longview\u2013Marshall, TX Combined Statistical Area. Discovery of oil near Kilgore, Texas in October 1920 was the beginning of an oil boom that attracted workers to the county and expanded the population by more than 500% by 1940, according to the census. By that time, the economy had stabilized but the East Texas Oil Field, extending in five counties, has continued to be important to the county and region's economy."