Book of Mormon Ancestry
Contrary to common belief, there is DNA and archaeological support for Israelite ancestry for some American Indians. This said, only a small proportion of the 15 million members of the Church (2013) would fit in this category.
Membership of the Church
When The Church of Jesus Christ of Latter-day Saints was first founded in 1830, the original members were of Western European descent. Early on, missionary work was performed among the Indian tribes, and there were a small number of members of African descent. Early in the history of the Church, missionaries were sent to the South Pacific, where Mormons now make up a large percentage of the population in some areas. Missionaries were also sent to Western Europe, and the strongest members of the Church, when westward migration to Utah began, were from the British Isles and Scandinavia. Indeed, these members were the backbone of the Church. Once the Church was established in the U.S., missionary work bore great fruit in Latin America. Many members of the Church are Spanish-speaking. The greatest growth at this point in time is in Africa and Asia. There are more LDS members outside of the United States than in it.
The Church as Israel
Most people who are attracted to the LDS Church are descendants from the tribes of Israel. Once in their lifetime, LDS members are priviledged to receive a Patriarchal Blessing which reveals to them their lineage in Israel. In the United States, most Latter-day Saints are descendants of Ephraim. In the Orient and among Native Americans, the most common lineage is of Manassah.