D&C 133

Not long after the Church was organized, the Lord revealed -

"...they who are in the north countries shall come in remembrance before the Lord; and their prophets shall hear his voice, and shall no longer stay themselves; and they shall smite the rocks, and the ice shall flow down at their presence.
27 And an highway shall be cast up in the midst of the great deep." (Doctrine and Covenants | Section 133:26 - 27)

"...even in Zion, by the hands of the servants of the Lord, even the children of Ephraim." (Doctrine and Covenants | Section 133:32)

For -

"Behold, this is the blessing of the everlasting God upon the tribes of Israel, and the richer blessing upon the head of Ephraim and his fellows." (Doctrine and Covenants | Section 133:34)

Over the years there has been much speculation concerning the lost ten tribes for one of our beliefs is -

"We believe in the literal gathering of Israel and in the restoration of the Ten Tribes..." (Pearl of Great Price | Articles of Faith 1:10)

There is much scriptural reference that the lost ten tribes presided over by Ephraim will return from the "north countries". My own opinion is that as the ten tribes were "lost" they moved to much of the countries in the northern hemisphere, particularly Europe. Many of these Europeans migrated to North America. In the early days of the Church we see masses of converts from the United States, Canada, and Great Britain. Most of these, including myself are so designated in patriarchal blessings of having the blood of Ephraim.

I believe that it is these people that are of the lost tribes of Israel that so readily heard and accepted His words.