When Joseph first brought the gold plates home from Cumorah, he told William that he could not view the golden plates but was allowed to reach into the case and feel what Joseph said were the plates.
William was baptized into the Church of Jesus Christ of Latter-Day Saints on June 9, 1830, by David Whitmer and left soon thereafter to serve a mission in New York and Pennsylvania. He followed The Church and settled in Kirtland, Ohio, in 1831. While there he was called to serve a mission in Erie County, Pennsylvania, in December 1832. During his mission he met Caroline A. Grant. The couple returned to Kirtland and were married on February 14, 1833. They would rear two children. In 1834, William was part of Zion’s Camp, a group of 200 men that were marching from Kirtland, Ohio to Clay County, Missouri, to try and help the Mormons there who were being violently persecuted and driven off their settlements. After the march disbanded he and the others returned to Kirtland. On February 15, 1835, he was called as a member of the Quorum of the Twelve Apostles of The Church of Jesus Christ of Latter-day Saints.
William’s fiery temper often carried him in a direction opposite the Church and his brother, Joseph. His headstrong attitude and passion either led him as a strong advocate of the Church, or turned him heavily against it. Although he repented of his attacks on Joseph, and was forgiven, his actions were never quite trusted by the main body of the Church.
In May 1838, William Smith left Kirtland with his wife and children and joined the church members in Far West, Missouri. While he was there the persecution he endured with the other church members increased his feelings of bitterness and resentment. On May 4, 1839, Smith and Orson Hyde were suspended from the Quorum of the Twelve by a vote of the church; however, Smith was readmitted to the Quorum on May 25. Later in 1839, he refused a call to serve with other members of the Twelve in England. Instead, he settled in Plymouth, Illinois.
From April to December 1842, Smith was the editor of The Wasp, a secular but pro-Mormon newspaper in Nauvoo, Illinois. Smith was fierce in his editorial criticism of the anti-Mormon newspaper the Warsaw Signal and its editor Thomas C. Sharp, whom Smith referred to in the Wasp as “Thom-ASS C. Sharp”. Smith resigned as the editor of The Wasp after he was elected to the Illinois General Assembly, where he served until 1845 He was also a member of the Nauvoo City Council
Following the Prophet’s death, William was supportive of the Quorum of the Twelve Apostles and their call to leadership. He was also told by Brigham Young that he had the right to be called as Patriarch of the Church: his father, Joseph Smith, Sr., and then his older brother, Hyrum, had served prior to their deaths. William accepted the call, but was not ordained until May 24, 1845, nearly a year after the death of Hyrum. Unfortunately, William soon began to presume upon his authority by claiming that his position gave him the right to be the next President of the Church. In October, 1845, William’s apostolic calling was revoked. He was excommunicated soon after and was furious toward the Church and its leaders. He joined briefly with the Strangite group.
In June 1845 he married Mary Jane Rollins but the marriage didn’t last. In May 1847, William married Roxie R. Grant, in Knox, Illinois. They would have two children before they divorced a few years later. In 1855, William moved back to Kirtland and attempted to start a new church with Martin Harris. While living in Kirtland, William married again to Eliza E. Sandborn on November 12, 1857 and would have three children. During the Civil War, William enlisted in the Northern Army and was stationed in Arkansas. In 1866, he and his family settled on a farm in Iowa. In 1878 he joined the Reorganized Church of Jesus Christ of Latter-day Saints but by 1891 he wasn’t affiliating with them anymore. In March 1889 his wife, Eliza died. At the end of the year he married Rosella Goyette on December 21, 1889, in Clinton, Iowa.
William lived longest of all the Smith brothers by nearly 50 years. Samuel Smith followed Joseph and Hyrum in death by just a month on July 30, 1844, after suffering from exposure and fatigue after the martyrdom of his brothers. Don Carlos and Alvin both passed away before them. William died at Osterdock, Clayton County, Iowa, on November 13, 1893, at the age of 82. He was survived by his sisters Sophronia and Katharine.