Prior to July 1, 1963, the Railroad Retirement Board (RRB) issued original SSN cards
in the 700 – 728 series to all railroad employees.
Beginning July 1, 1963, SSA began assigning SSNs to railroad employees from the regular
series; and, we stopped issuing SSNs from the 700 series until October 2000, when
we activated the 764 and 765 series for assignment to the general public.
Beginning June 25, 2011, SSA randomly assigns all SSNs. SSA decided to include all
unassigned numbers from the 700 series in the pool of numbers available for assignment
purposes. Thus, the pool of numbers available for assignment now include all previously
unassigned numbers from the RRB series (700-728).