The U.S. Social Security Death Index is a well-known resource for research to look for persons who were registered for a Social Security Number at time of death. The Index is no longer currrently maintained for the public. You could try https://www.familysearch.org/search/collection/1202535 for a version that was current as of 2014. See https://en.wikipedia.org/wiki/Social_Security_Death_Index for more information.
