The institution, originally referred to as California State Prison-Imperial South, was renamed Centinela State Prison by the Imperial County Board of Supervisors. Centinela State Prison was named for Mount Signal, the mountain located on the US Mexico international line once used to watch over the state's borders to prevent unauthorized passage into the US. Centinela is the Spanish word for "Sentinel" or signal. The institution, originally referred to as California State Prison-Imperial South, was renamed Centinela State Prison by the Imperial County Board of Supervisors. Centinela State Prison was named for Mount Signal, the mountain located on the US Mexico international line once used to watch over the state's borders to prevent unauthorized passage into the US. Centinela is the Spanish word for "Sentinel" or signal.