When Catherine Weldon (Jessica Chastain) arrives in Standing Rock in “Woman Walks Ahead,” it’s arguable whether‎ it was the train that brought her there or her own head of steam. Driven by the desire to paint a portrait of Sitting Bull, she is undeterred by a not-so-friendly word of warning from a colonel (Sam Rockwell) who joined her in the dining car on the way over or the far quieter intimidation of being in a town where the women stay inside. In South Dakota for the freedom she saw in pictures of the legendary Sioux chief while running out the clock on a loveless marriage in New York, it is to some dismay that is far from the feeling she gets once actually there, especially when she is able to actually speak to Sitting Bull, who isn’t moved by her interest in him.

Nonetheless, “Woman Walks Ahead” ‎has that ineffable airiness about it that Weldon is chasing, a breezy Sunday matinee feeling as a film that isn’t weighted down by the tragic history it recounts. A little more than a decade removed from the Battle of Little Big Horn when Sitting Bull famously prevailed over a cocksure Custer, the film finds the chief pressed into another fight to protect Native Americans from getting their land carved up further by the U.S. government in the Allotment Act, using tribal food rations as leverage. Although Weldon will insist to anyone who asks that she’s just there to paint pictures, ultimately paying Sitting Bull for the privilege of immortalizing him on an oil canvas, she inadvertently becomes a go-between who can buy supplies at the general store without the limits placed on Native Americans and a voice of reason for when tempers flare. It’s an ideal role for Chastain, luminous in radiating both Weldon’s ferocity and unadorned admiration of Sitting Bull, who is played with gravitas but also an ingratiating lack of pretense that makes the burgeoning friendship between the two feel so authentic and delightful to watch unfold.

The film is also a surprisingly good fit for director Susanna White, who is known for rigorous dramas (save for breaking into features with “Nanny MacPhee Returns” after an accomplished career in TV), yet shows a lightness of touch and a sense of scale that proves invaluable for “Woman Walks Ahead,” capturing the grandeur and allure of the West without romanticizing it‎. Unfussy cinematography from Mike Eley and a pleasingly twangy score from‎ George Fenton‎ ease one into the lilting rhythm of life on the open range while a seasoned supporting cast that includes Rockwell, Ciaran Hinds and Bill Sage ground the film as formidable adversaries as various extensions of the government aiming to do what they need to to secure Native American consent for the Allotment Act, some by more violent means than others. Yet without putting too fine a point on it, “Woman Walks Ahead” draws a parallel between the marginalization that both Weldon and Sitting Bull have faced because of their gender and race, respectively, that has given both the ability to see beyond the men that stand before them in opposition as part of a longer continuum, knowing that perhaps they are limited in what they can achieve, but in time the resistance to them will shrink as well. White, Chastain and company have the same understanding in illuminating a relationship that may have been short-lived yet meaningful, the result is all the more powerful because of it.

“Woman Walks Ahead” does not yet have U.S. distribution.