Teresa - There are a couple of ways to approach this.But first, not everyone is listed in the SS Index.She may have been a federal employee and never paid into the social security system. (Federal employees paid into a separate retirement system).It's also possible that she died before completing the application for a SSN.The law was passed around 1935, but not everyone applied right away, especially unemployed women. The fact that she was unmarried increases the odds of her not being listed in the index.Typically, women outlive men and are entitled to SS benefits upon the death of the husband (assuming the husband paid into the system).This is true for women, regardless of whether they actually worked or paid into the system.
Here are a few far-flung search techniques you can try when you hit a wall.But a warning is in order – they can be time-consuming.
-On the random chance she did marry, you might try searching the SS index for any person named Kathryn (leave last name blank) but enter Kathryn's known month/year of birth.Her SS number was likely issued in DC since that's where she lived just before the requirement came about.You can further restrict the results by selecting DC as the issuing state.With that list, you can begin ruling out some by searching for obits or locating them in the available census records.This could be quite a job in itself, especially if your list of Kathryns is a long one.
-Search for an obit for her sister Teresa.Most obits list survivors and the location of the survivor.If survivors are listed but no mention is made of Kathryn, you can safely assume she died before Teresa.That fact allows you to narrow down the range of years in which she could have died.
-If you can't find her in a census record, try using alternate spellings for her first name (Catharine, Catherine, Katharine, Katharyn, etc.)Try also using wild card spellings (Kath* and Cath*).Search also under nonconforming diminutives – Kitty, Kit, etc.Do the same for her last name.Search under names that could have been misspelled by the census taker – Goff, Golf, Guff, etc.Search also under look-alike names that could have been mis-transcribed – "Cough" for Gough, Gouth, Gaugh, etc.As you go about that, keep in mind that census records are replete with errors.If no one was home when the censustaker called, the information would sometimes be supplied by neighbors.Frequently that information could be wildly off.
-Don't limit your search to DC proper.People moved with ease across the DC-Maryland and DC-Virginia lines.It's also possible that she returned to Baltimore or even Pennsylvania.So you may need to widen your net a bit before you conclude that she died early.
You may have already tried these things and if you have, odds are good that she did, in fact, die early.