is not a perfect film, but it's an important one. The film — narrated in a low-key way by co-director Ben Knight — tracks America's love affair with river dams and hydroelectric power — from its progressive, put-people-to-work origins under Roosevelt in the 1930s to its obsession with damming every possible river in the '50s and '60s under the sometimes shaky premises of flood control. The small state of Maine has over 800 dams, to cite one example.