The plains of Nephihah were the open ground near the Nephite city of Nephihah, on the east borders by the seashore. The city itself was founded around 72 B.C. on a site between the cities of Moroni and Aaron, joining the borders of the two, during Captain Moroni’s fortification of the eastern lands (Alma 50:14).
Around 62 B.C. the Lamanites under Amalickiah took the city of Moroni, and those who fled gathered at Nephihah with the people of Lehi to meet the Lamanites in battle; Amalickiah then took Nephihah as well, along with the other cities along the east seashore (Alma 51:23–24). When the Lamanites under Ammoron later attacked the people of Nephihah, who had gathered from the cities of Moroni, Lehi, and Morianton, the survivors fled and joined Moroni’s army, and the city was lost (Alma 59:5–11).
Moroni and Pahoran marched to retake the city, pitching their tents in the plains of Nephihah near it. When the Lamanites would not come out to fight on the plains, the Nephites scaled the wall by night with cords and ladders, let themselves down on the west where the Lamanites were not camped, and attacked at morning. The Lamanites fled out by the pass; the Nephites took the city without the loss of one soul and killed or captured many. The Lamanite prisoners afterward joined the people of Ammon (Alma 62:14–30).