Many references in the Book of Mormon indicate that the Nephites held the priesthood—that is, they had the power and authority to act in the name of God. However, the Book of Mormon does not refer specifically to the two major divisions in the priesthood, the Aaronic Priesthood and the Melchizedek Priesthood. Thus the question has frequently arisen as to exactly what priesthood was held by the Nephites. Joseph Fielding Smith gives his answer in the following comprehensive statement:
The Nephites were descendants of Joseph. Lehi discovered this when reading the brass plates, He was a descendant of Manasseh, and Ishmael, who accompanied him with his family, was of the tribe of Ephraim. Therefore there were no Levites who accompanied Lehi to the Western Hemisphere. Under these conditions the Nephites officiated by virtue of the Melchizedek Priesthood from the days of Lehi to the days of the appearance of our Savior among them. It is true that Nephi “consecrated Jacob and Joseph” that they should be priests and teachers over the land of the Nephites, but the fact that plural terms priests and teachers were used indicates that this was not a reference to the definite office in the priesthood in either case, but it was a general assignment to teach, direct, and admonish the people. Otherwise the terms priest and teacher would have been given, in the singular. Additional light is thrown on this appointment showing that these two brothers of Nephi held the Melchizedek Priesthood, in the sixth chapter, second verse of 2 Nephi, where Jacob makes this explanation regarding the priesthood which he and Joseph held: “Behold, my beloved brethren, I, Jacob, having been called of God, and ordained after the manner of his holy order, and having been consecrated by my brother Nephi, unto whom ye look as a king or a protector, and on whom ye depend for safety, behold ye know that I have spoken unto you exceeding many things.”This seems to be a confirmation of the ordinations that he and his brother Joseph received in the Melchizedek Priesthood. All through the Book of Mormon we find references to the Nephites officiating by virtue of the Higher Priesthood after the holy order. Alma, discoursing on the subject before the people of the city of Ammonihah, said: “And again, my brethren, I would cite your minds forward to the time when the Lord God gave these commandments unto his children; and I would that ye should remember that the Lord God ordained priests, after his holy order, which was after the order of his Son, to teach these things unto the people.” (Alma 13:1. See also D&C 107:1-4.)
In the opening verses of Alma, Chapter 43, Mormon records the following: “And now it came to pass that the sons of Alma did go forth among the people … and … they preached the word, and the truth, according to the spirit of prophecy and revelation; and they preached after the holy order of God by which they were called.”
From these and numerous other passages we learn that it was by the authority of the Melchizedek Priesthood that the Nephites administered from the time they left Jerusalem until the time of the coming of Jesus Christ. By the power of this priesthood they baptized, confirmed, and ordained. During these years they also observed the law of Moses. They offered sacrifice and performed the duties which in Israel had been assigned to the priests and Levites. They observed in every detail the requirements of the law. When the Savior came to them, he fulfilled the carnal law and did away with the sacrifice by the shedding of blood of animals. He informed the Nephites that in him the law of Moses was fulfilled.
When the Savior came to the Nephites, he established the Church in its fulness among them, and he informed them that former things had passed away, for they were all fulfilled in him. He gave the Nephites all the authority of the priesthood which we exercise today. Therefore we are justified in the belief that not only was the fulness of the Melchizedek Priesthood conferred, but also the Aaronic, just as we have it in the Church today; and this Aaronic Priesthood remained with them from this time until, through wickedness, all priesthood ceased. We may be assured that in the days of Moroni the Nephites did ordain teachers and priests in the Aaronic Priesthood; but before the visit of the Savior they officiated in the Melchizedek Priesthood. (Answers to Gospel Questions, 1:124-26.)