I worked as a claims rep for Social Security for a year and a half.
It is true that Social Security numbers, the first three digits did tell where you lived when you applied for a number. We had a chart which showed each number and where they originated.
At one time the middle two were always even except for 1-10. I think so many were issued that they changed that some time ago.
The last four were simply random.
“The last four were simply random”
When I got my SS card, in the 50’s, my friend and I applied together and were given our cards. Her number is exactly the same as mine except the last four...mine was one number below hers....example, 1587 and 1588....