Mont. Code Ann. § 7-34-4101

In case of necessity, the city or town council has power to establish, at a suitable place within or without the limits of the city or town, a hospital to prevent the spread of smallpox or other contagious or infectious diseases, to regulate the control thereof, to do all other acts which may be necessary for the promotion of health, and to prevent the spread of infectious or contagious diseases within the city or town.