In April, 1911, it was announced that the Joplin Police Department had adopted a “metropolitan police” scheme of equipping the police officers with whistles. Viewed as one more step toward imitating the police departments of large cities, the whistles were thought useful:
“Although it is seldom that an occasion arises in this city when an officer cannot take care of himself, it is thought best to be on the safe side. When an officer hears one of these whistles, which are of a peculiar tone, he is to hasten at once to the scene of conflict, or wherever the sound comes from.”
It was thought at the time that the presence of a mere whistle may have prevented some of the deaths of Joplin’s police officers up to that point. It’s unknown if the whistle dramatically changed the safety of the police in a city with the rowdy reputation of a mining town.
Source: Joplin News Herald