The most common cause of death in 1900 was influenza accompanied by pneumonia. By then there were 38 states with state boards of health. County health departments began to emerge as the need for local health departments was realized. The first county health department was set up in Jefferson County, Kentucky, in 1908. Public health efforts to control diseases, such as utilizing filtering water systems, were effective.
- ELLIS H., JOHN. Medicine in Kentucky. Kentucky: University Press of Kentucky, 2009.