The “Explorer-Doctors”: Searching for Rocky Mountain Spotted Fever in Montana’s Bitterroot Valley

In southwestern Montana, a steep, forested valley extends for 96 miles from the city of Missoula, framed to the west and east by the Bitterroot and Sapphire mountain ranges.  Historically the home of Flathead (or Salish) and Nez Perce tribes, it was crossed by the Lewis and Clark Expedition as it searched for the overland route across the Rocky Mountains.  On September 11, 1805, the Corps of Discovery spent “a Beautiful pleasant morning” in the area gathering their scattered horses and keeping a wary eye on nearby Indian encampments. They found the climate mild and the land abundant with cherries.


The Bitterroot Valley.

One hundred years later, a new corps of explorers would retrace Lewis and Clark’s descent into the Bitterroot, and like their predecessors, were mandated by the government to solve a uniquely American problem.  However, these explorers were not surveyors, soldiers, field scientists, or botanists.  They were doctors, tasked with finding and eliminating the scourge of the American northwest, Rocky Mountain Spotted Fever (RMSF).  While previous studies about the medical battle against RMSF have made mention of the Bitterroot Valley’s passing connection to the Lewis and Clark saga, it has been purely in brief exposition.  This article seeks to highlight this story’s peculiarity in comparison to other disease-fighting missions, and how that peculiarity may have sprung from an exploratory spirit inherited from the Corps of Discovery.

Rickettsia rickettsii, the bacteria known to be the main causative agent of RMSF, is tick-borne and cannot be transmitted between humans.  The disease is characterized by a high fever, chills, muscle pain, and a distinctive full-body rash.  In the early twentieth century, the Bitterroot Valley was selected as ground zero for RMSF research due to the unusual severity of the disease in that region.  In 1929, for example, Dr. Roscoe Roy Spencer recorded that the mortality rate for victims in the Bitterroot Valley ranged from 76-89%, whereas in the Snake River Valley of Idaho, the infection killed only 5%.

Rickettsia rickettsii

Rickettsia rickettsii

The history of the disease in the area was short but turbulent.  200 cases of a mysterious ailment locals nicknamed “blue disease” or “black measles” occurred in the Bitterroot Valley from 1873 to 1901. In March of 1901, the Montana state legislature created a State Board of Health, and Governor Joseph Kemp Toole assigned its new secretary, Dr. A. F. Longeway, to investigate the problem.  Over the next three decades, a steady line of doctors journeyed into the valley to personally investigate the origin of a disease which came to be known as Rocky Mountain Spotted Fever.

In May 1902, with help from the Minnesota State Board of Health, Dr. Louis B. Wilson and Dr. William M. Chowning arrived in the Bitterroot to start a scientific study on the fever.   Wilson and Chowning assumed roles as surveyors by distributing area maps to local physicians that were marked with the names of every known fever victim.  The doctors then personally investigated every case they could find, even journeying to the most remote cabins in the canyons.  Those whose work required prolonged outdoor exposure, such as timber cruisers and forest rangers, were found to be most susceptible to the illness.  When Wilson autopsied a five-year old girl who had “small wounds of the skin due to tick bites” he became interested in the possibility that RMSF was insect-borne. Unfortunately, Wilson abandoned his investigation after opting to take a job at the Mayo Clinic in Rochester, Minnesota.


Dr. Howard T. Ricketts.

In 1906, a young doctor named Howard T. Ricketts came to the Bitterroot Valley to study the fever. Driven by “a burning desire to help humanity,” Ricketts began a three-year investigation of the disease, finally proving in a crude, temporary laboratory that Wilson’s hunch about the ticks was correct.  At least a half-dozen more doctors (several of whom succumbed to the disease themselves) entered Montana in subsequent years, carrying out field experiments on tick eradication and vaccines.

Dr. Spencer arrived in 1922. His studies reveal that the explorer-doctors intensively documented RMSF’s effect on wild fauna. He wrote that “the Columbian ground squirrel, the pine squirrel, the yellow-bellied chipmunk, the woodchuck, the side-striped squirrel, the badger, the jack rabbit, the weasel, and the prairie dog are susceptible to the disease.”  Domestic animals that were immune but carried the ticks on their fur were also scrutinized.  The Montana State Board of Entomology eventually ordered the “dipping” domestic stock, a ghoulish practice through which sheep and cattle were soaked in a mixture of washing soda, white arsenic, pine tar, and water that burned the ticks off of their hides.

Like the Lewis and Clark Expedition, RMSF research was driven by a desire to examine and rectify myth through systematic scientific study.  The practice of mapping, recording, and disseminating the macroscopic facets of the disease enabled the doctors to uncover its origins.  There is little room for explorer-doctors today.  While RMSF research advanced knowledge on pathology in a time when the medical community urgently needed it, the behavior displayed by the investigating doctors has rarely been replicated in other major American epidemic investigations.  Health workers’ reluctance to treat AIDS patients in the 1980s and early 90s, for example, stands in stark contrast to the RMSF doctors’ willingness to enter the remote, fever-ridden forests of western Montana.  Today’s globally connected world has also seen a rapid development in quarantine policy, so while the explorer-doctor spirit may still live on in the men and women fighting Ebola at its source, scrutiny and precaution offer a special set of challenges to these medical workers.


Philip A. Kalisch, “Rocky Mountain Spotted Fever: The Sickness and the Triumph,” Montana: The Magazine of Western History, Vol. 23, No. 2 (Spring, 1973), pp. 44-55

“Rocky Mountain Spotted Fever,” Public Health Reports (1896-1970), Vol. 27, No. 33 (Aug. 16, 1912), p. 1341

“Rocky Mountain Spotted Fever in Montana,” Public Health Reports (1896-1970), Vol. 32, No. 26 (Jun. 29, 1917), p. 101.

R. R. Spencer, “Rocky Mountain Spotted Fever,” The Journal of Infectious Diseases, Vol. 44, No. 4 (Apr., 1929), pp. 257-276




One thought on “The “Explorer-Doctors”: Searching for Rocky Mountain Spotted Fever in Montana’s Bitterroot Valley

  1. Pingback: “One Feeble Leper” – Imperialism and Public Health in Territorial Hawaii | The History Bandits

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