The first minute or so of Down the House, Tricia Murajda’s wonderful new documentary — debuting Fri., May 14 at the Philadelphia Independent Film Festival — looks like the dream for any out-of-town politician. Featuring old footage from workers at the Leviathan Mill in Braddock, Pa., it is a walking embodiment of every image people from outside the region have of Western Pennsylvania: gritty, hard-working steel towns that are a foundation for blue-collar jobs. The reality is more complicated. “Outside of this region, I noticed that there’s very much a misunderstanding, and at times even a contempt, for this region and for the people of this region,” Murajda said in an interview with