One hundred years ago, dams were seen as examples of great design and celebrated for making it possible to get cheap power and turn sprawling deserts into green suburbs and farms.

Now, as tens of thousands of dams start to reach the end of their lifetimes, attitudes have dramatically shifted: People are realizing that many dams don’t actually work that well, and they’ve destroyed river ecosystems. The new solution, at least in some places, is packing old dams with dynamite and obliterating them.

Once you start paying attention, you start seeing dams everywhere.

A documentary called DamNation takes a look at the story of dams in the United States, from the building boom of the 20th century to the beginning of the removal boom today, complete with spectacular footage of a dam blowing up with 800 pounds of explosives. Filmmakers Ben Knight and Travis Rummel got in a rented camper van in the summer of 2011 and started to drive around the country looking at some of the 75,000 larger dams.

The filmmakers worked with biologist Matt Stoecker and Patagonia founder Yvon Chouinard, who originally came up with the idea for the movie; Patagonia produced it and has been screening it at their retail stores as part of a long-standing push for dam removal.

“Dams tend to be part of the landscape that you just don’t notice,” says Rummel. “But once you start paying attention, you start seeing them everywhere.”

Though dams were built for a variety of reasons–a small fraction generate power, and others were meant to help with preventing floods, storing water, or providing irrigation–the film explains that most are incredibly expensive to maintain for the value they provide. Billions of dollars have been spent just on trying to save the salmon that can no longer travel upstream because of them.

As the huge concrete structures start to reach the stage where they’d need major renovations to keep operating, many dam operators are deciding it makes more sense to tear them down. The filmmakers hope to help that process along.