For more than a century and a half after the Mountain Meadows Massacre, no one knew exactly where the bodies were buried.

A California-based archaeologist now says he has solved the mystery, and that it was surprisingly easy.

Last summer, Everett Bassett found what he believes are the two rock graves constructed by the U.S. Army about 20 months after Mormon militiamen and their Paiute allies slaughtered 120 westbound Arkansas migrants in southwestern Utah.

The sites are 1,000 or more feet to the west of monuments The Church of Jesus Christ of Latter-day Saints built on properties it acquired under the belief that they harbored the grave sites, Bassett said. He used Army records to locate the actual graves, which were described simply as mounds of rocks. They are in a ravine formed by the Old Spanish Trail — exactly where the records said they would be — on land the church does not own.

"The trick to finding these was figuring out where the road was," Bassett said. "I was sitting on it when I realized that this enormous mound of rocks is what we were looking for all these years."

He unveiled his findings Saturday at a gathering of victims' descendants in Harrison, Ark., and plans to publish them in a peer-reviewed journal.

"I wanted to go through the descendant groups and have them have the first shot at preservation," Bassett said. "They need stabilization, and we can't do that without public involvement and public or private funding."

Richard Turley, assistant LDS Church historian and co-author of the critically acclaimed 2008 book "Massacre at Mountain Meadows," said he's eager to see Bassett's report.

"If, in fact, they have found the graves, it would be a very important development, one that would be of great interest to many people," he said. "People have looked for it for many, many years."

Victims' descendants were pleased by Bassett's discovery.

"It just adds to getting closure. These people have been dead 150 years. There's not a lot you can do for them, but you can remember them in the highest way possible," said Phil Bolinger, president of Mountain Meadows Monument Foundation Inc. "We believe the site is worthy for a national monument. That would be the highest order of federal protection."

The LDS Church-owned site was designated as a national historic landmark in 2011, but Bolinger contends the graves mark the locations where the massacre actually occurred. They are about a mile north of the siege site, which is accurately marked with the monument built in 1990.

Bolinger's group is working with the property owner, whom he declined to name, to craft a conservation agreement.

Though the events leading up to the Sept. 11, 1857, massacre have been the subject of controversy, it's generally believed that Mormon militiamen disguised as American Indians besieged the Fancher-Baker wagon train for several days before John D. Lee brokered a truce.

The militiamen, who included prominent pioneers and church officers, guaranteed the migrants safe passage if they laid down their arms and followed them north.

The migrants agreed, only to be lured to their deaths. On a predetermined signal, the militiamen shot the men and boys in the head at one location and bludgeoned the women and children at another.

Only 17 children, those under age 6, were spared. The dead were left where they fell or received cursory burials.

For months, the corpses lay beside an important pioneer migration route, prompting the Army to dispatch 207 soldiers to construct a more worthy resting place for the Mountain Meadows victims.

The church did not fully acknowledge its members' role in the crime until 2007. Lee, who died before a firing squad 20 years after the killings, was the only one held accountable.

Bassett describes the Army-built structures as "sepulchers," both 8 by 12 feet, formed by boulders of basalt and granitic material — even though the surrounding rock is almost all sandstone.

Soldiers probably hauled the rock a short distance to the massacre site because it was seen as a more suitable building material, Bassett said. These different rocks provide further proof that the bones of up to 100 victims rest under them.

He believes the soldiers would have constructed the sepulchers in a single day. They gathered what bones they could, interred them in the structures and covered them with 4 feet of rocks.

"They were really more functional and designed to keep wolves from digging them up," Bassett said. "They were not built where people would see them."

The grave for the men and boys has a stone apron around it, along with a sandstone tablet, which Bassett believes was inscribed with axle grease that faded long ago.

For years, people had assumed the Army-built graves to be conspicuous monuments that had been dismantled and scattered through the years.

The piles did not fit with what Bassett expected to find. Dirt is now piled along the structures' sides, and sagebrush grows on top of them.

"There's no way this could be the grave," Bassett said, "but, on other hand, there was absolutely nothing else it could be."

He has made no effort to disturb the rock structures, which are characteristic of the mass graves the Army built for Civil War dead. Bassett has never seen one like these before in the West.

"We want to preserve and protect the sites," Bolinger said. "The Army did a wonderful job of building the sepulchers, but the creek is different than it was 150 years ago."

He also believes the LDS Church has some explaining to do.

"It makes us want to say to the church, you either intentionally didn't tell us or you weren't as thorough as we thought you were capable of," he said. "You guys have bought all this property and built monuments that missed the mark. You made two mistakes."