High Quality Content by WIKIPEDIA articles! O. B. Ellis Unit (E1, previously Ellis I Unit) is a Texas Department of Criminal Justice prison located in unincorporated Walker County, Texas, 12 miles (19 km) north of Huntsville. The unit, with about 11,427 square feet (1,061.6 m2) of space, now houses up to 2,400 male prisoners. Ellis is situated in a wooded area shared with the Estelle Unit, which is located 3 miles (4.8 km) away from Ellis.