As I hope to do more regular posting on here again this year, I'm going to start using many of the posts to discuss different resources for genealogy online and give some background and tips on using these sources.
One of the glaring mistakes I've noticed many genealogists make is finding and/or relying on sources that they don't understand. As I've mentioned in past posts, it is important that you understand at least a little bit about the source you are using. For example, it would be helpful to know that census records in the U.S. have been done every 10 years, that the 1890 records were mostly destroyed in a fire, and that they release census records after 72 years. (The 1950 census will be released to the public in 2022.) For the census, it would also be helpful to know that they were subject to many errors, either by the census taker or because of which individual in the house was relaying the information to the census taker. Knowing these things can help you determine how best to use the census in your research, and to remind you that you'll want to verify information you find in a census with vital records whenever possible.
The Social Security Death Index is one of the most common sources where I see mistakes made, so we'll start there. The Social Security Death Index is a federal database kept by the Social Security Administration. Social security numbers began to be issued in 1935, after the passing of the Social Security Act. Many amendments have been made to the act since that time. Social security numbers were not required for everyone, and in fact, still aren't. If you don't ever work a job where payroll taxes would be withheld from wages, you can actually get through life without a social security number. However, it would make it very difficult to maintain a living, get a driver's license, open a bank account, apply for a loan, or buy a home, so I don't recommend it.
There were many people who were already past the retirement age when the law was passed in the 1930s who never did sign up for a number. I've found many ancestors or relatives who died after the act was passed who never applied for a number or received benefits. So this index is one you'll only want to use for more recent relatives. In addition, it was common up until about 1986 (a tax law that was passed that year) that people didn't apply for a number until they were at least 14 and ready to start earning income. Since that time, the IRS requires social security numbers to be listed when claiming someone as a dependent on a tax return, so it's very common now to apply for a number for a child with the birth certificate filing.
When it comes to genealogical purposes, the first thing to know is that the Social Security Death Index, or SSDI, only lists information for individuals whose death was reported to the Social Security Administration. (This may seem obvious at first glance, but trust me, I've seen people trying to search the SSDI for someone that is still alive.) Since 1973, it is estimated that the SSDI contains anywhere from 93 to 96% of the deaths of individuals aged 65 or older. So it is a very useful tool. However, just because you don't find someone in the database doesn't mean they didn't have a social security number. Again, there are some that are never reported.
The database itself is free to search. It is available on many genealogy websites, including FamilySearch and Ancestry.com.
The database normally lists the person's given name and surname, date of birth (sometimes), month and year of death, the social security number, the state or territory where the number was issued, and the zip code of the last known residence of the individual. If I don't have a death date or place for someone, I use the SSDI first to see if I can narrow down a death date, which will then allow me to find a death certificate.
One extremely important thing to note is that the surname of the person will be whatever they listed on their original application (or changed to, later). In other words, for the most part, a woman will be listed with her last married name. Unless a woman never married, it is rare for a woman to be listed by her maiden name. This is important, as it can be easy when using the SSDI to confuse individuals with the same given and surnames. Whatever the name was at death is most likely how it will be listed in the SSDI.
In addition to this, if you find a record for a relative in the SSDI, you can actually request a copy of the original SS-5 application for social security number. This document might list further details, including birthplace, father's name, and possibly even mother's maiden name.
If you have a request for me to review a particular database or record type, drop me a message or leave a comment, and I'll add it to my queue.