The Sea West is a significant body of water mentioned in the Book of Mormon and serves as the western boundary of the Nephite and Lamanite lands at certain periods in their history. This sea is noted as being bordered on the east side by a narrow strip of wilderness that also reached to the east sea, forming a natural demarcation between the lands southward and northward (Alma 22:27).
Throughout the Nephite record, the presence of the Sea West signifies the vastness of the Nephite territory and the expansion of the people. At one point, it is indicated that the Nephites had prospered and expanded their settlements to cover the entire face of the land from the Sea South to the Sea North, and from the Sea West to the Sea East, demonstrating a considerable population growth and geographical reach (Helaman 3:8; Helaman 11:20).
The text implies that the landmass itself might not have been oriented directly north-south or east-west, but at an angle, such that there could actually be a sea to the north and a sea to the south of portions of Nephite and Lamanite lands at different points in the Book of Mormon chronology (Helaman 3:8). The Sea West is indirectly alluded to in these references, helping to frame the lands occupied by these two groups of people throughout their history.