A legion of FamilySearch.org volunteers have manually indexed the 1940 census line by line to come up with a searchable database of the census records. Though the entire country has not (as of today) been completely indexed, Minnesota and Iowa are complete and ready to search.
If you’d prefer to download images of the census (so you can see the actual form that was carried by the census-taker), I made a list of links to each county/district.
2 Responses to 1940 census now indexed and searchable