The supply side is taken care of. There's a finished film, scripted by Bill Kauffman and starring (among others) Billy Campbell, Angus McFadyen and Peter Fonda.
Demand? Well, that's the catch. It looks like a great movie and I wouldn't be surprised to see it on some awards lists, but historical dramas can be a tough sell to local cinemas. They're usually longer than your run-of-the-mill "troubled but sexy and dedicated cop/soldier/spy/bureaucrat catches half the bad guys and kills the other half" clones, which means fewer screenings per day, which means less money, especially if they're not blockbuster hits from the git-go.
Copperhead is a movie you're going to want to see on the big screen ... and you need to let your local theater know you want to see it on the big screen.
Fortunately you can to that very easily -- here, or by clicking on the movie poster in the sidebar.
If you're not sure you want to see it, why not check out the trailer? Here ya go: