Smoot was born in 1862 in Salt Lake City, Utah Territory. He was the son of a Mormon pioneer from Kentucky and Iowa, Abraham O. Smoot, who was a mayor of the city from 1856 to 1862. His mother was Anne Kristina Morrison Smoot, also known as Anne Kirstine Mauritzen before her marriage. Anne Kristina Morrison Smoot was Smoot's father's fifth wife of six plural marriages and 27 children, three of whom Abraham O. Smoot adopted. The family moved to Provo, Utah, when his father was called by Brigham Young to head the stake there. Smoot went to school at the University of Utah (then a religious school) and graduated from Brigham Young Academy (now Brigham Young University) in Provo in 1879. After school, Smoot worked as a Mormon missionary in England. After returning to Utah, Smoot married Alpha M. Eldredge of Salt Lake City on September 17, 1884. They had six children together. Thereafter, Smoot became a successful businessman in the Salt Lake City area. In 1895, he became very involved in the government of the LDS Church and achieved more authority. On April 8, 1900, Smoot was chosen as an LDS Church apostle and member of the church's Quorum of the Twelve Apostles.