There are 15 US Post Offices in Grayson County serving a total of 93,471 residents equating to 6,231 residents per post office. It's estimated that approximately 149,190 packages are handled across the 15 county post offices annually. Grayson County is a county located in the U.S. state of Texas. As of the 2010 census, its population was 120,877. The county seat is Sherman. The county was founded in 1846 and is named after Peter Wagener Grayson, an attorney general of the Republic of Texas. Grayson County is included in the Sherman-Denison, TX Metropolitan Statistical Area, which is also included in the Dallas-Fort Worth-Arlington, TX Combined Statistical Area. It is also part of the Texoma region, with proximity to both Lake Texoma and the Red River."