THE STORY of the American wild horse, for two hundred years or more, has in fact been two tales, a simultaneous duplicity: vaunted icon of freedom; scapegoat, victim, villain. As hunting quarry and as helpmeet, these animals have long incurred horrific injustice, which has been the catalyst for numerous cris de coeur: the 1961 movie The Misfits, Marguerite Henry’s beloved Mustang, Hope Ryden’s The Last Wild Horses, and, now, Deanne Stillman’s powerful Mustang. Let us hope the latter does not suffer the fate of its predecessors: functionally ignored. If so, America’s wild horse soon will be gone.

The mustang is unaware of its most important service: “being wild and free for the rest of us.” But it surely knows we treat our symbols with greater concern than the reality from which they derive. Here, three hundred pages of proof.

The book’s beginning, the compendious history of the horse in the New World, foreshadows its end: an alternate title might simply be Death, Death, Hideous Death. It starts so dispiritingly that the sensitive reader may wish to stop. But Stillman’s talent as a writer makes this impossible, to the mustang’s benefit.

After the Spanish conquerors reintroduced them to America, horses eventually flourished in the West to the point that by the 1840s their wild herds were spectacularly vast. This largely meant only that more of them could be captured, tamed, used in war and to rope the frontier, and also exterminated like the vermin they are still often believed to be.

This may or may not have been a matter of good fortune for a particular mustang who became known as Comanche. Here we climb Stillman’s narrative to a breathtaking height over a panoramic tragedy: when the smoke of carnage lifted over a place named Little Bighorn, the last one standing was this horse.

It is with stories like this — of a quintessential America peopled by Buffalo Bill, hardscrabble cowboys, John Wayne the one and the many — that the author builds a case for mythology as stage curtain for the real drama: destruction of entire genealogies, from Native American to native fauna. We valorize an image, plaster it on everything from products to state legends, while blithely exterminating its source. Says Stillman, the U.S. government’s crusade, begun against indigenous peoples, has extended to such creatures as wolves and wild horses, whose herd numbers may already have been reduced beyond recovery.

There comes a point in every murder mystery film when, heart in throat, we cover our eyes. We know what will happen, and the knowing is almost as bad as watching the unspeakable. Stillman’s description of The Misfits (written, alas, from life by Arthur Miller) — a movie too painful for me to watch — is an appropriate prelude to the crescendo of her Part III, “Last Stand.” Here is where it gets real, dizzyingly real, and you uncover your eyes even though you can barely stand to.

In researching the murders of two Nevada women for her book Twentynine Palms, Stillman learned about the brutal killings of thirty-four mustangs there in 1998. Although these were at the hands of some unhinged individuals, as she discovered, our government is continuing the work. Wild horses are seen as competition for western livestock (who are probably the primary destroyers of riparian and grassland habitat) grazed on public lands by way of taxpayer subsidy.

We project onto the horse our own warring emotions, especially our guilt. And then we do away with it. Symbol, indeed. As Stillman writes, “America is bleeding.” In the case of the mustang, it is right from the heart.