Rocky Mountain spotted fever (RMSF), or "black measles," fatal in eighty percent of adult cases, plagued early-day settlers in the Bitterroot Valley. In 1906 Howard Ricketts identified ticks as carriers of this disease. State efforts to control the insects were only partially successful, and in 1921 the U.S. Public Health Service agreed to fund a vaccine development program. An abandoned schoolhouse across the river was converted into a laboratory where Drs. Ralph R. Parker and Roscoe Spencer developed an effective RMSF vaccine. Its manufacture required large-scale tick rearing under makeshift conditions, which resulted in tick-related illnesses among the technicians and two deaths from lab-acquired RMSF. In 1927, the State Legislature authorized construction of a new research facility. Despite local opposition, this laboratory opened in 1928 and soon gained national significance when RMSF was diagnosed in the eastern United States. In 1938 Dr. Harold Cox developed an improved method for RMSF vaccine production in embryonated chicken eggs. By 1940 the facility included ten buildings, and research was expanded to include the study of other insect-borne diseases. During World War II, the lab manufactured typhus and yellow fever vaccines for the military, producing and distributing 3,360,000 doses at peak production in 1945. After World War II, the need for RMSF vaccination diminished with the discovery of broad-spectrum antibiotics. The death of Dr. Parker in 1949 brought the pioneer era of RMSF research to a close, but Rocky Mountain Laboratories continues to pursue research on immunologic, allergic, and infectious diseases.