In 1947, the U.S. federal government and thirteen state governments launched a broad campaign to eliminate malaria in the southeastern region of the country by reducing the mosquito population. The initiative relied heavily on the use of the chemical pesticide dichloro-diphenyl-trichloroethane (DDT). Developed in the 1940s, DDT was one of the first widely used insecticides. It was highly effective at killing mosquitos and other insects. However, over time it was discovered that the chemical was poisonous to humans and other mammals. DDT also became less effective over time as insect populations became immune to the pesticide.