With epidemiology in the news it might be timely to note that the first historical event affecting Granite County for which we have a solid date is the smallpox epidemic of 1782. This event is stated in Salish accounts to have wiped out a band of their tribe in the Bitterroot. The incident occurred at the tail end of a smallpox epidemic that raged during the Revolutionary War and gradually spread across the North American continent from 1775 to 1782. The British indeed used smallpox as a form of biological warfare against the Colonial army.
The effects in the Northwest US and northern plains areas are perhaps best known from David Thompson’s accounts, particularly in the stories related to him by members of the Blackfeet nation. They told David they had caught the disease because they plundered a Shoshoni camp where practically all the Shoshoni were dead or dying from smallpox. The result was so devastating that the Blackfeet for a time reconsidered their traditional aggressive war policies since they apparently suspected that the epidemic might be spiritual payback for their constant attacks on their neighbors… what in today’s parlance we might call “karma”.
The 1782 smallpox is only one of several cataclysmic epidemics that wiped out most of the native population of the Northwest and northern plains. The later waves of smallpox apparently affected every tribe with the exception of the Flathead (Salish), who acquired immunity via a vaccination program instituted by the Jesuit missionaries under the direction of the noted doctor Father Ravalli.
In addition to smallpox, the Northwest was ravaged by epidemics of measles and malaria. The measles outbreak led to the killing of missionaries in Washington State who lacked the tools to prevent or cure the disease and so were blamed for the numerous deaths by the local tribes. Malaria broke out in Washington state in 1829 when trading ships from the tropics inadvertently transported malarial mosquitoes into swampland along the Columbia River. Because of somewhat unusual weather conditions the area was temporarily suitable for breeding of these tropical insects. Fatalities among native tribes ranged up to 100 percent and a 95 percent death rate was typical. It is likely that Montana, at least, was spared this particular epidemic thanks to the cooler climate.