The Sea West marked the western edge of the lands held by the Nephites and Lamanites. A narrow strip of wilderness ran from the sea east to the sea west and divided the Lamanite lands from the land of Zarahemla, separating the two peoples (Alma 22:27).
As the people multiplied and spread from the land southward to the land northward, they came to cover the land from the sea south to the sea north and from the sea west to the sea east (Helaman 3:8). After later rebuilding their waste places and prospering again, the people of Nephi again spread across the whole land, on the north and the south, from the sea west to the sea east (Helaman 11:20).
The reach from the sea south to the sea north alongside the reach from the sea west to the sea east suggests the lands were oriented at an angle rather than squarely along the cardinal directions, so that a sea lay to the north and to the south of portions of the land at different points in the record (Helaman 3:8).