In 1896, Rocky Mountain spotted fever was first recognized in the Snake River Valley of Idaho and was originally called “black measles” because of the characteristic rash. By the early 1900s, the geographic distribution of the disease encompassed parts of the U.S. from Washington and Montana to California, Arizona, and New Mexico. In response to this severe problem, the Rocky Mountain Laboratory was established in Hamilton, Montana.

Howard T. Ricketts was the first to identity the infectious organism that caused the disease (Rickettsia rickettsii). Between 1981 and 1996, this disease was reported from every U.S. state except Hawaii, Vermont, Maine, and Alaska.