[Kleon]

When I arrived in the US in 1971 and was issued my SSN# it was explained to me that the 1st few numbers identified the state that the number was issued from

Yes, but not necessarily the state in which you reside.

[Exmil_UK]

What circumstances would a normal citizen have that would make a young adult have a different mailing address form their residential address?

College would be understandable, for example a California SSN prefix would have made sense for Obama.

Given the geographical distance involved, why would Obama aged 17 use a mailing address in Connecticut when he was resident in Hawaii (the state where he first worked)?