The death of a Montana dam.

On March 28 in Milltown, Mont., the waters of the Clark Fork and Blackfoot rivers breached a coffer dam to flow freely through their confluence for the first time in a century. The moment came at the midpoint of a $100 million Superfund cleanup of contaminated sediments at the Milltown Reservoir—perhaps the most ambitious environmental remediation project ever attempted in the country. When the cleanup began in 2006, a Slate slide show looked at the history of the dam and the memories attached to the landscape it created.

Click here to read a follow-up slide-show essay on the passing of Milltown.