When 844 people died in the Chicago River in the Eastland disaster, the event devastated Chicago and shook the nation. Lookingglass’ 2012 production of Eastland resurrected the ghosts and events of that day in a stunning folk musical. Artistic Director Heidi Stillman sat down with playwright Andy White and co-composer Andre Pluess to talk about why they approached this forgotten calamity, and the journey to bring it to fruition in a production TIME called “remarkable.”