CARROLLTON, Ark. — On the wildflower-studded slopes of the Ozarks, where memories run long and family ties run thick, a little-known and long-ago chapter of history still simmers.

On Sept. 11, 1857, a wagon train from this part of Arkansas met with a gruesome fate in Utah, where most of the travelers were slaughtered by a Mormon militia in an episode known as the Mountain Meadows Massacre. Hundreds of the victims’ descendants still populate these hills and commemorate the killings, which they have come to call “the first 9/11.”

Many of the locals grew up hearing denunciations of Mormonism from the pulpit on Sundays, and tales of the massacre from older relatives who considered Mormons “evil.”...

There aren’t many places in America more likely to be suspicious of Mormonism — and potentially more problematic for Mitt Romney, who is seeking to become the country’s first Mormon president. Not only do many here retain a personal antipathy toward the religion and its followers, but they also tend to be Christian evangelicals, many of whom view Mormonism as a cult....