Moroni was a Nephite city built by the east sea, on the south by the line of the Lamanite possessions. The Nephites laid its foundation and named it Moroni (Alma 50:13). A second city, Nephihah, was later founded between the city of Moroni and the city of Aaron, joining the borders of the two (Alma 50:14).
The Lamanites came into the land of Moroni, in the borders by the seashore, while the Nephite commander Moroni was suppressing the king-men and preparing for war. The Nephites in the city were not strong enough to hold it, and Amalickiah drove them out and took the city and all its fortifications. Those who fled went to the city of Nephihah, while the people of the city of Lehi gathered to meet the Lamanites in battle (Alma 51:22-24). The people of Nephihah were drawn from the cities of Moroni, Lehi, and Morianton, and were later attacked by the Lamanites (Alma 59:5).
In the closing campaign of the war, Moroni’s forces drove the Lamanites until the survivors fled into the land of Moroni by the seashore. Moroni pursued them from city to city until he met Lehi and Teancum, and the Lamanites fled to the land of Moroni, where their armies gathered in one body under their king Ammoron. Moroni, Lehi, and Teancum encamped around the borders of the land, hemming the Lamanites against the wilderness on the south and east (Alma 62:25-34).
At the death of Christ, the city of Moroni sank into the depths of the sea and its inhabitants were drowned (3 Nephi 8:9; 9:4).