Throughout MSP's history, it was referred to as "the prison without walls" due to the dispersed camps within its property. Hugh Ferguson, the director of public affairs of MSP, said that the prison is not like Alcatraz, because it is not centralized in one or several main buildings. Instead MSP consists of several prison camps spread out over a large area, called "units". Each unit serves a specific segment of the prison population, and each unit is surrounded by walls with barbed tape.