Until the 1960s, measles was a fact of life in the United States and the developed world. Each year, about half a million people-mostly children-would come down with symptoms that were no worse than a bad cold, except for a rash that spread over the body. Most thought it was harmless, but each year, a small percentage of those that got it died. A look into its history shows that measles has been one of history's deadliest killers, virtually wiping out entire Native American populations in colonial America. Since a vaccine was developed, the number of measles cases each year has become a fraction of what it once was. This is the fascinating story of this once-feared disease-from its ancient origins to the discovery of a vaccine and near eradication.