Texas State Penitentiary at Huntsville or Huntsville Unit (HV), nicknamed "Walls Unit", is a Texas state prison located in Huntsville, Texas, United States. The approximately 54.36-acre (22.00 ha) facility, near downtown Huntsville, is operated by the Correctional Institutions Division of the Texas Department of Criminal Justice.[1] The facility, the oldest Texas state prison, opened in 1849