Joseph Smith in 1834 and the revelation he received about Zelph also speaks to the location of Book of Mormon lands.
On the top of the mound were stones which presented the appearance of three altars having been erected one above the other, according to the ancient order; and the remains of bones were strewn over the surface of the ground. The brethren procured a shovel and a hoe, and removing the earth to the depth of about one foot, discovered the skeleton of a man, almost entire, and between his ribs the stone point of a Lamanitish arrow, which evidently produced his death. Elder Burr Riggs retained the arrow. The contemplation of the scenery around us produced peculiar sensations in our bosoms: and subsequently the visions of the past being opened to my [Joseph Smith's] understanding by the Spirit of the Almighty, I discovered that the person whose skeleton was before us was a white Lamanite, a large, thick-set man, and a man of God. His name was Zelph. He was a warrior and chieftain under the great prophet Onandagus, who was known from the Hill Cumorah, or eastern sea to the Rocky mountains. The curse was taken from Zelph, or, at least, in part - one of his thigh bones was broken by a stone flung from a sling, while in battle, years before his death. He was killed in battle by the arrow found among his ribs, during the last great struggle of the Lamanites and Nephites. (History of the Church, 2:79-80; June 3, 1834). 
Where Was Zelph Killed?
According to the History of the Church 2:78-79 Zelph was found buried in a high mound (above the tops of the trees) on the banks of the Illinois River in the State of Illinois. This is not far from present day Florence, Illinois, which is about 75-100 miles north of St. Louis, where route 100 crosses the Illinois River. The mound that Joseph Smith dug into on June 2, 1834 is still there and is one of about 35 bluff top mounds covering about a mile along the river. Archaeologists estimate that it dates from between 50 BC and 50 AD, based upon the style of the artifacts found in it and the age of nearby mounds which have been radiocarbon dated from 50 BC to 250 AD. This dating alone raises significant questions about Zelph's involvement in any Hill Cumorah battles, but this is a different subject.
The "last great struggle of the Lamanites and Nephites" allegedly occurred in 385 AD (Mormon 6:1-15) at Hill Cumorah. If Hill Cumorah was in the Mexico-Guatemala-Honduras area then Zelph would have had to travel roughly 1,800 miles one way to return to the spot where the Mormons found his bones. If Hill Cumorah is near Palmyra, NY, the travel distance would be over 700 miles. While over 700 miles is a long distance in the days of traveling by foot, it is more reasonable than 1,800 miles.
How likely is it that a man who got an arrow between his ribs at Hill Cumorah in the Mexico-Guatemala-Honduras areas, or the Palmyra, NY area, would then travel roughly 1,800 or 700 miles to die? No, the bones of the man Joseph Smith dug up must have been killed near where Smith found him. It does not seem likely that Zelph's friends or comrades carried him to the banks of the Illinois River. They would be looking out for their own lives. Moreover, according to Mormon 6:15 and 8:2, the Nephites as they escaped went southward, not northward from Mexico-Guatemala-Honduras to the banks of the Illinois River roughly 1,800 miles away.
Mormon apostle and historian Joseph Fielding Smith in his book Doctrines of Salvation, Vol.3, pages 232-243 also relates the history about Zelph and provides additional evidence why the Book of Mormon lands are in the continental United States. In addition he says that the Hill Cumorah located in New York State, near Palmyra, NY, is the place where the great extermination battle (Mormon 6:9-15, 8:2-3) took place.
While there is evidence that Joseph Smith later also gave other locations for Book of Mormon lands (Kenneth W. Godfrey, BYU Studies, Vol. 29, No. 2, page 48), none of this sets aside Smith's clear statements allegedly made by the power of God. As a reminder, the following was said, "The Book of Mormon is a record of the forefathers of our western tribes of Indians;....." by the "commandment of God," "revealed to the Prophet Joseph," "made known to Joseph," "that God was so mindful of us as to show these things to His servant. Brother Joseph had inquired of the Lord, and it was made known in a vision" all of which placed Zelph and Book of Mormon lands in the continental United States. While Smith might have changed his mind, there is no evidence that God did.
Why is it so many Mormons (like FARMS) try to place Book of Mormon lands in the Mexico-Guatemala-Honduras area while Joseph Smith by the power of God said they were in the continental United States?
Even dust wouldn’t collect there!