There are 2 US Post Offices in Dallam County serving a total of 11,492 residents equating to 5,746 residents per post office. It's estimated that approximately 18,343 packages are handled across the 2 county post offices annually. Dallam County is a county located in the northwestern corner of the U.S. state of Texas. As of the 2010 census, its population was 6,703. Its county seat is Dalhart. The county was founded in 1876 and later organized in 1891. It is named for James Wilmer Dallam, a lawyer and newspaper publisher. Dallam is the northernmost of the ten Texas counties that from 1885\u20131912 constituted the legendary XIT Ranch. The ranch is still celebrated through the XIT Museum in Dalhart and the annual XIT Rodeo and Reunion held the first long weekend in August."