Before the time when death certificates list cause of death, it can be difficult if not impossible to determine how an ancestor died. Is it possible that there are clues in your ancestor's estate settlement to his or her final illness?
The probate of Paul Freund in Davenport, Iowa, in the early 1860s indicates that several prescriptions were purchased from a local druggist in the month before he died. These are all listed by prescription numbers, except for one--juniper berries, which were purchased the day before he died. How much of a clue it is his case is not known, but it's made me go back and look at a few other estate settlements to see if types of drugs are listed in the final set of bills to be paid.