From deadly outbreaks of yellow fever and influenza to the development of the nation’s oldest quarantine station and a vaccine for polio, Pennsylvania has been the site not only of destruction caused by deadly epidemics but of innovations in public health that arose in response to them. The latest issue of Legacies, inspired by the 100th anniversary of the 1918–19 flu pandemic, looks back on a century of crises and achievements in Pennsylvania’s public health history.