 As recently as 1978 the prison held only about 1,600 prisoners in 2,000 available cells distributed among five major cellblocks of 400 cells each.The five major cellblocks were supplemented by about 40 cells in a security unit known as BAU (Behavior Adjustment Unit) or RHU (Restricted Housing Unit); this unit included a special death row section (though executions were never carried out at this prison).The original 1929 plan for the facility included eight major cellblocks of 400 cells each, or 3,200 individual cells.