This is another good secondary source for placing your ancestors in a certain area at a certain time. If your ancestor is listed as the owner of one of these companies you can write that company to see if it still exists and if it is still owned by part of your family. Check out the want adds and personals. You might get lucky and find a reference to one of your ancestors buying or selling something. Again a secondary source but every scrap of info helps.
Lets turn to the Obits.
This will tell you not only who died, but in many cases the names of the survivors, their relationship to the deceased and the pallbearers. Birth and Death dates of the deceased, names of brothers and sisters and grandchildren. It can also be used to verify death dates of the surviving relatives. Since the Pallbearers are frequently family friends instead of family members you need to check all of the obits to see if they can help you place an ancestor in a certain time and place. If you are chasing a 20th century ancestor the addition of sports pages in small town papers can be an untapped gold mine.