There are 3 US Post Offices in Dimmit County serving a total of 9,834 residents equating to 3,278 residents per post office. It's estimated that approximately 15,696 packages are handled across the 3 county post offices annually. Dimmit County is a county located in the U.S. state of Texas. As of the 2010 census, its population was 9,996. The county seat is Carrizo Springs. The county was founded in 1858 and later organized in 1880. It is named for Philip Dimmitt, a major figure in the Texas Revolution. The spelling of the county name and the spelling of the individual's name differ because of a spelling error in the bill creating the county name."