The Narrow Pass was a passage at the borders of the land Desolation, in the narrow neck of land between the land southward and the land northward. It led by the sea into the land northward, with the sea on the west and on the east (Alma 50:34).
When the people of Morianton fled toward the land northward, Moroni sent an army under Teancum to stop them; Teancum headed them off at the narrow pass on the borders of Desolation, slew Morianton, defeated his army, and took the rest prisoner (Alma 50:33-35). Moroni later ordered Teancum to fortify the land Bountiful and secure the narrow pass that led into the land northward, so the Lamanites could not seize that point and attack on every side (Alma 52:9).
In the final Nephite-Lamanite wars the pass was a boundary line: the Lamanites gave Mormon’s people the land northward as far as the narrow passage leading into the land southward, and received the land southward in exchange (Mormon 2:29). Mormon afterward gathered his people at the land Desolation, to a city in the borders by the narrow pass which led into the land southward (Mormon 3:5).