Today, the SSDI is searchable on a few places on the Internet. The one I prefer using is at Ancestry.Com. You can use it either for "blind" searches, along the "show me all the Warners in Connecticut", or to find a specific individual.
The SSDI index can be used in several ways for locating an individual.
For instance, if you know your grandmother died in Iowa, but are not sure where she was born, you could verify her place of birth.
Let's say that you live in Missouri, and that you don't know where your grandparents are from. Your name is KLIPPER, and you know your grandfather was named Harry. Search the SDDI for "Harry Klipper" without listing a state, and you would learn that there were 2 Harry Klippers who died from New York. Perhaps you could then use the information to search the Census in New York and see if one of these Harry Klippers had children you could identify.
You could do a search only on Surname, such as the KLIPPER example above, and learn that most of the 76 KLIPPERs in the index lived in New York or New Jersey.
But what comes next is better!
After you have identified your ancestor, perhaps a grandparent, in the SSDI, you can send a letter to the Social Security Administration, along with $7, and they will send you the application for Social Security Number that your ancestor filed. Besides giving their birthdate and address, it will list the mother and father's name, and often many other details as well!
If you use the Ancestry.com SSDI search engine, the "Write Letter" button on the results will produce a letter to the SSA requesting the information on your ancestor. Print the letter and attach your check for $7, and in approximately 20-30 days, you will receive their application!
I hope this has been helpful. Send me an email and let me know.
Send mail to: Gary Warner