Three Mile Island, Pennsylvania, was the site of the United States’ worst nuclear accident. Luckily, no radiation was released into the environment and no one was killed. In March 1979, the nuclear reactor at the Three Mile Island plant overheated, breaking the radioactive rods. Pennsylvania’s governor recommended a voluntary evacuation of pregnant women and preschool children who lived within five miles (8 kilometers) of the plant. It was the unexpected self-evacuation of residents in the area that created major problems. The evacuations yielded surprising information about the lack of preparedness of communities for such an event, and have led to increased planning and preparedness for nuclear accidents and evacuations.