the original SSN format was
regional zone of issuance 3 digits
year of issuance 2 digits
sequence number in that zone/year 4 digits
Hence nnn-nn-nnnn
Not that much to work with eh?
Looks like bozos patterned it after the Bell Phone number system: area-exchange-phone but thats nnn-nnn-nnnn
I feel Cobol was involved here.