The new documentary Lakota Nation vs. United States chronicles the Lakota people’s struggle to reclaim the Black Hills, the Native American tribe’s sacred land that was stolen away from them by the U.S. government, who violated a series of treaty agreements with them — including the Fort Laramie Treaty of 1868, which was supposed to ban white settlement on the Black Hills. Then gold was discovered there, and all hell broke loose.

Directed by Jesse Short Bull and Laura Tomaselli, and produced by Sarah Eagle Heart, Mark Ruffalo, and Marisa Tomei, the IFC Films doc also tackles America’s history of exploiting the Native American people, and what can be done to try to right past wrongs.

“My personal connection roots back at least five generations, since the time of my great-great-grandfather who was alive during the treaties, turmoil, and warfare in this area,” Jesse Short Bull, a member of the Oglala Lakota Tribe, tells Rolling Stone. “All of this history is in my DNA, in my blood, alongside an inherent respect for the land that is deeply meaningful.”

Ruffalo, the Oscar-nominated actor and star of various Marvel superhero films, is an ardent activist who’s lent his support to anti-fracking efforts and to the Standing Rock Reservation’s opposition to the Dakota Access Pipeline (the Lakota’s Black Hills are in this land).

“I have worked shoulder to shoulder with our Indigenous fellow citizens beginning with the fight against fracking in New York State,” offers Ruffalo. “That campaign lead me to the historic events that occurred at Standing Rock in 2016. I made dear friends there and came to know and fully understand the injustice suffered by our Native Americans. One of those greatest wrongs was the theft of sacred spaces through the breaking of treaties. These treaties were made between two sovereign Nations, and have not been honored by the United States. This film, made by Lakota people, tells us the Lakota part of that story.”

Ruffalo adds, “Since Standing Rock, there has been an incredible explosion of Native stories written and made by Native filmmakers and populated by Native actors. Even at this moment, we are dubbing The Avengers in the Lakota language, with me and the cast joining.”

Hollywood’s history of depicting Native Americans, however, is an ugly one. Native Americans have long been depicted in Hollywood films and television projects as either bloodthirsty barbarians or noble savages.

“Hollywood, in the past, has done much harm to the Native people by too often portraying them using ugly caricatures, missing their dignity, their traditions, their incredible resilience, and their deep reverence for the land and water, the living creatures and the family of humankind,” Ruffalo says. “We are in the Native American Century, the 7th generation, and it couldn’t be more timely and important that we bring this dark secret of the U.S.A. to justice.”

Watch an exclusive trailer for Lakota Nation vs. United States here. The film will open in New York theaters on July 14, and in Los Angeles on July 21: