“September Dawn” records a little-known footnote to the bloody settling of the frontier, the Mountain Meadows Massacre of 1857, which some describe as the first act of religiously inspired mass murder in U.S. history.

While resting in Utah before making the final push to California, a wagon train of 120 settlers was ambushed by fanatic Mormons, who slaughtered, man, women and children alike. The facts of the case are not in dispute, but the film already has stirred controversy with its critical portraits of the church’s early leaders and its graphic, unsparing depiction of the bloodbath.

Its Christian settlers are bathed in such a flattering glow of sanctity, and the Mormons portrayed as such inhuman zealots, that the project has the appearance of melodramatic sectarian propaganda. LDS prophet Brigham Young (Terence Stamp) is presented as the cold-blooded architect of the atrocity, and the fact that the massacre took place on Sept. 11 is driven home forcefully.

As Mormon Bishop Jacob Samuelson, Jon Voight delivers thundering sermons against the gentiles (the church’s term for those who don’t share their faith) who used violence to drive his people into exile in the West years earlier, and views the pioneer women who wear practical male clothes and carry firearms as blasphemous abominations.

The film is rife with scandalized references to polygamy and proto-feminist indignation about the status of Mormon women, while director Christopher Cain makes it clear where he stands by photographing Mormon characters from the most menacing angles he can find. Samuelson’s boy Micah (Taylor Handley) practically licks his chops in delight as he cuts down his helpless victims while disguised as an Indian.

The only decent Mormon in the bunch is his older brother Jonathan (Trent Ford), redeemed by his love for the devoutly Christian Emily (Tamara Hope). The film feels less like historical drama than a venomous religious tract printed on celluloid. Rated: R for violence. Rating: 1 star.