Pesticides kill bugs, but what else do they do? Rachel Carson explained the dire consequences of our reliance on chemicals in her 1962 book Silent Spring. Spring was silent because no birds sang. Their eggs were all damaged by DDT, a pesticide in wide use at the time. Carson's plea to treat the environment with care resonated with a lot of people, including JFK.

The Kennedy administration launched an investigation of chemical pesticides, and its report credited Carson with setting off the alarm bells. Silent Spring became an international bestseller, helping create a receptive atmosphere for Johnson's environmental proposals.

Carson didn't live to see the Great Society's anti-pollution and conservation efforts. She died of breast cancer a month before LBJ made his speech at the University of Michigan.