When Kevin Costner first reached out to Sienna Miller about playing a pioneer in his four-movie, three-decades-in-the-making passion project, Horizon: An American Saga, the actor was flattered. She had been such a fan of Dances With Wolves—Costner’s Oscar-winning 1990 directorial debut—that she’d named her pet rabbits after two of the film’s characters. But the British-bred Miller also wasn’t entirely sure why the iconic actor set his sights on her for his Western franchise.
“It felt so random, but of course if you get a call saying, ‘Kevin Costner wants to talk to you’—I didn’t want to question it too much,” she tells me on Zoom. (In a statement to VF, Costner explains why he cast Miller: “She has obvious natural beauty, but she has a nuance in her roles that I admired and appreciated. She passed the ultimate test for me because she is believable.”)
In the Civil War–era epic, which opens in theaters Friday, Miller plays a young mother who, after uprooting her family and moving out West, loses both her husband and son. But her Frances is a survivor; devastated as she is, she soldiers on.
“There’s a toughness and a resilience” to the character, Miller says. “But I think in that period, when you’ve suffered this unimaginable loss, which was not uncommon, you had one choice: to survive and thrive and move on with your life.”
Miller has proven her own hardiness in contemporary Hollywood. She overcame fame’s worst early-aughts byproducts: voracious paparazzi, phone hacking, and a hideous medical-privacy invasion when she was only 23. At the time, she was dating her Alfie costar Jude Law, who was so movie-star hot that tabloid coverage of the relationship overshadowed and undermined Miller’s nascent career.
“I was very desperate to be taken seriously because I had a huge amount of fame before I’d ever had a film come out,” says Miller, who had made only one mainstream movie before Alfie—2004’s Layer Cake. “It was a constant battle against the perception that I was something frivolous, perhaps, or someone’s girlfriend.”
She proved otherwise by successfully taking Rupert Murdoch’s News Group Newspapers to court twice—the first time before she turned 30. In June 2011, she received a formal apology from its News of the World tabloid, acknowledgment of phone hacking, and damages, helping to precipitate the publication’s shutdown the following month. A decade later, Miller won substantial damages from the publisher after alleging that The Sun pushed her into decisions about a pregnancy, which she ultimately terminated, when the tabloid discovered the news by allegedly illegal means. (As a term of the settlement, NGN did not admit any liability.)
Even so, Miller has spent much of her film career in the lead-actor penalty box, wringing what she can from peripheral parts as wives, girlfriends, and mistresses in Oscar-nominated films like American Sniper and Foxcatcher. When she’s landed leading roles with actual room for range on either stage or screen, she’s earned excellent reviews. See: Tippi Hedren in The Girl; Maggie in Cat on a Hot Tin Roof; Sally Bowles in Cabaret; a blue-collar grandmother grappling with her daughter’s disappearance in American Woman; and a politician’s spurned wife in Anatomy of a Scandal. Though Miller is only one of dozens of characters in Horizon: An American Saga – Chapter 1, her performance as a grieving mother is the emotional standout.
About a month after the first Horizon film premiered to an 11-minute standing ovation at the Cannes Film Festival, Miller logged on to Zoom from a hotel room in Los Angeles, where the youngest of her two daughters was napping. In hushed tones, the actor discussed fulfilling her ’90s dream of working with Costner, surviving early-aughts stardom and scandal, and fighting for more of the types of roles she deserves.
Vanity Fair: I read that on your first Zoom with Kevin, he ended the conversation by telling you that he would show you an American West you’ve only dreamed of.
Sienna Miller: Yes. He said, “Will you go West with me?”
Did he deliver on his promise?
He really did. My whole concept of America had been so New York to LA and a little bit in between, but I’d never really explored the West apart from California. But the middle of Utah [where Horizon was filmed] is the most extraordinary place. Even flying over the Rocky Mountains and imagining that that route was traveled with wagons and children…it was an unfathomable achievement to get across the country.