SALT LAKE CITY — It has been more than half a century since the last big shift in thinking about where events in The Book of Mormon took place, but a dramatically different — and disputed — theory is gaining traction among some of the Mormon faithful.

The theory, popularized on Web sites and at conferences by advocates Rod Meldrum and Bruce H. Porter, suggests that events in The Book of Mormon took place in the heartland of the United States, east of the Mississippi River from the Great Lakes to the Gulf of Mexico.

“The word is out now. There is a movement going through the church,” says Porter, a former LDS institute teacher who lives in Arizona and leads Mormon-themed tours.

For the first 100-plus years of Mormonism, most believers assumed the ancient civilizations described in The Book of Mormon ranged over the entire Western Hemisphere. The “narrow neck” between “land north” and “land south” described in the sacred text was assumed to be the isthmus of Panama.

But, in the 1950s, careful reading of the text led scholars to propose a more limited geography; since then, most of the dozens of theories have focused on “Mesoamerica,” a region that includes southern Mexico, Guatemala, Belize and the northwestern part of Honduras and El Salvador in Central America.

Much of The Book of Mormon centers on the Nephites, who left Jerusalem for the Americas about 600 B.C., according to the text. In what the church calls the book's “crowning event,” Jesus appeared to the Nephites after his resurrection in order to re-establish his church; the Nephites later fell victim to their own wickedness.

Mormons believe an off-shoot of the Nephites, the Lamanites, are ancestors of Native Americans. The histories of the Nephites and other civilizations form the basis of The Book of Mormon, which was revealed to the prophet Joseph Smith in 1823.

The Church of Jesus Christ of Latter-day Saints long has held that God has not revealed the exact geography described in The Book of Mormon, and the church has no official position on where, in the Americas, the ancient civilizations lived and died.

Most LDS scholars still believe Mesoamerica is more plausible because it fits the scriptural text and archaeological and anthropological evidence that has been found through the years.

Meldrum and Porter, meanwhile, come at the question from a different angle, and that's the source of the controversy.

Though they claim archaeological and DNA evidence for their model, they start with what they say are 36 clear “prophecies and promises” in The Book of Mormon and statements by Smith, indicating he believed the history unfolded in what would become the United States.

Scholars who cling to a Mesoamerican model must disregard what the church's founding prophet said, Porter said.

“Most of the people fighting it are people who have something to lose financially or by reputation,” Porter said.

Not only does that assertion anger critics, who say it unfairly casts them as apostate, they argue it is flat wrong.

“They are trying to put us down when that's not at all what we believe,” says Steve Carr, a retired pediatrician who is senior vice president for the Book of Mormon Archaeological Forum, whose Web site has featured a series of articles refuting the claims of the heartland advocates.

Smith may have alluded to the United States as the home of the Nephites, but he also wrote near the end of his life, Carr says, that the history took place in Central America.

“He was just guessing like a lot of other people,” Carr says. “A lot of things they take as revelation are just ideas, not revelation at all.”

Not so fast, says Porter, who believes the statements supporting Central America were written by Smith's colleagues rather than the prophet himself.

“He (Smith) either knew, or he didn't know. If he didn't know, what was he doing?”