This database is current up to the 28 Sep 2009 release of the SSDI distributed by the Social Security Administration and contains a listing of individuals whose last known residence, or last Social Security benefit, was in Iowa County. The National SSDI is available at other locations on the Internet. A good source of information can be found at Social Security Death Index Guide.
"The Death Index contains a listing of persons who had a Social Security number, who are deceased, and whose death was reported to the Social Security Administration. (The information in the Death Index for people who died prior to 1962 is sketchy since SSA's death information was not automated before that date. Death information for persons who died before 1962 is generally only in the Death Index if the death was actually reported to SSA after 1962, even though the death occurred prior to that year.)" - Social Security Online FAQ