A California-bound wagon train of about 140 Arkansas emigrants led by John Baker and Alexander Fancher camped near the present-day southwestern Utah town of Enterprise in September 1857. Fears the U.S. Army was preparing to forcibly remove Brigham Young as Utah territorial governor and impose martial law were at their height. Spurred by inflammatory sermons of LDS leaders, a siege mentality focused Mormon resentment toward the "gentile" wagon train.
Early on Sept. 7, a group of American Indians and local Mormon "Indian missionaries" attacked the encircled wagon train without warning. After the Arkansas party repelled the offensive, a contingent of Mormon territorial militia, acting on orders from religious leaders, joined the assault, which dragged on four more days as 15 emigrant men were killed while fighting or escaping to summon help.
With their ammunition, food and water almost gone, the emigrants were persuaded by Mormon officials on the afternoon of Sept. 11 to surrender their arms in exchange for a safe escort past the Indians to Cedar City. Segregated into groups of young children, women and teens, and adult males, they were led under heavy guard by more than 50 militiamen and settlers out of the corralled wagons and up the valley.
On a pre-arranged command, the rescuers turned upon the emigrants, joined by Indians who had been lying in wait. Estimates of the death toll include 14 Arkansas men shot in the head, 12 women and 35 youngsters clubbed or knifed to death, with 17 children younger than age 8 surviving the double-cross.
Nine cowhands hired to drive cattle also were murdered, along with at least 35 other unknown victims. In all, 120 people, mostly women and children, were slain.
After two decades of rumors, denials, cover-ups and failed indictments, one of the participating Mormon leaders, John D. Lee -- Young's adopted son -- was tried, convicted and executed by firing squad in 1877 at the scene of the massacre. Lee considered himself a scapegoat.
No one else was ever officially held responsible for the crime.
Here's another brief article about the massacre, which includes a description of it from Roughing It by Mark Twain. The American Heritage article says that section was removed from later editions of the book.
The issue, of course, is culpability. The Mormon Church denies any responsibility for the massacre, although evidence exists linking church leadership, including Brigham Young himself, to the event.
Does theocracy ever work to the ultimate good of human welfare? I don't think so.