According to John Sorenson, the land of Shemlon was clearly the Lamanite base in the times of Zeniff, Noah, and Limhi; attacks on the Zeniffites always came from or through Shemlon. Supposing that the city of Lehi-Nephi was Kaminaljuyu, at present-day Guatemala City, the land of Shemlon would be the present-day Amatitlan lake-side gateway to the Valley of Guatemala through which forces from the lush piedmont area would have approached the city. Shemlon's attractiveness to the Lamanite elite would have included its climate, significantly warmer than at Kaminaljuyu which was 1,600 feet higher, yet not so oppressively hot as the adjacent lowlands, the old Lamanite base. The border between the land of Shilom and the land of Shemlon would obviously be the sharp bluff overlooking what is now lake Amatitlan and the curving Villalobos River. Near the river the Lamanite poachers could conveniently have got at the Nephite flocks, while the bluff would have been an ideal spot for Zeniff's watchmen. [John L. Sorenson, An Ancient American Setting for the Book of Mormon, pp. 169-171]
“I Had Sent My Spies out Round About the Land of Shemlon”
That Zeniff "had sent my spies out round about the land of Shemlon" (Mosiah 10:7) to warn of an invasion out of the land of Shemlon implies that the land of Shemlon was close. Zeniff's use of spies at this point in time is significant because it is reported directly after Mosiah 10:6, which says that "king Laman died . . . and [his son] began to stir his people up in rebellion against my people [the people of Zeniff]." Perhaps Shemlon was the name Zeniff gave to that portion of the original "land of Nephi" that had been taken over by the Lamanites. It seems that Shemlon was the place from which a Lamanite king ruled. At this time, there is not one passage indicating that the Lamanite king resided in any city or land called Nephi. Later on, however, the city of Nephi is the location of the king of the Lamanites (compare Mosiah 24:2; Alma 20:8; Alma 22:1; Alma 47:20-21). Also, why would the Nephites keep referring to a "land of Nephi" that as time goes on apparently becomes much larger and almost completely populated and dominated by Lamanites? I doubt that the Lamanites would have used the term "land of Nephi" to describe any of their own lands. [Alan C. Miner, Personal Notes]