About the Social Security Death Index (SSDI)
The Social Security Death Index (SSDI) is an index of more than 70 million deceased people who had social security numbers and whose deaths were reported to the social security administration. Here is some information about the SSDI, courtesy of searchforancestors.com:

You can use the SSDI to:

• Find the birth and death date of the deceased
• Identify the last place of residence to help know where to search for a death certificate, obituary, or will
• Identify the place where the death benefit payment was sent, which could help locate living relatives. The benefit information will indicate where the recipient of the death benefit lived, which is not necessarily the same place as where the deceased lived.
• Determine the state where the social security number was issued which may give another area to search records. This is the state where the deceased applied for his social security number, most likely when he/she first got his first job or where he was working when social security was started. It may or may not be same as birthplace.
• Use the social security number to request more information from the Social Security Administration. (SS-5 form). This application form should include the site where the application was made, parents' names, date and place of birth.
• Locate lost relatives who have died.

• Have information about birthplace, spouse, or children.
• Have information on deaths before 1962 when the index was computerized.
• Have information on those whose deaths were not reported to the SS even if the death occurred after 1962.
• Have information on those who did not have a Social Security number because they were Federal or state employees who had their own retirement program.