The Seventh-day Adventist Church pioneers were members of Seventh-day Adventist Church, part of the group of Millerites, who came together after the Great Disappointment across the United States and formed the Seventh-day Adventist Church. In 1860, the pioneers of the fledging movement settled on the name, Seventh-day Adventist, representative of the church's distinguishing beliefs. Three years later, on May 21, 1863, the General Conference of Seventh-day Adventists was formed and the movement became an official organization.
The Seventh-day Adventist Church had its roots in the Millerite movement of the 1830s and 1840s, during the period of the Second Great Awakening, and was officially founded in 1863. Prominent figures in the early church included Hiram Edson, James Springer White and his wife Ellen G. White, Joseph Bates, and J. N. Andrews.
Many of the Adventist pioneers first began their work when they were teenagers. When the Seventh-day Adventist Church was newly formed, it was teenagers and young adults who held many leadership positions and helped to build up the church. Pioneers such as Ellen Harmon White, John Loughborough, J. N. Andrews, and Uriah Smith were teenagers and young adults when they began making an impact in the Seventh-day Adventist Church, many starting even before in the Advent movement started by William Miller.
Willim Miller was a farmer, and Baptist preacher, who, from 1831 to 1844 began the Millerite movement, preaching the imminent return of Christ. After the War of 1812 he was converted and began a systematic study of the Bible and in the process he discovered the prophecies of Daniel and Revelation, especially Daniel 8, which seemed to predict that Christ would soon return to earth. Hundreds of ministers and laymen joined in preaching the message. By the expected time for Christ's return, Miller had between 50,000 and 100,000 followers, commonly known as Millerites. After the disappointment of October 22, 1844, which Miller and many of the leaders of the first movement accepted as the date, groups of Millerites formed what later became the Seventh-day Adventist Church. Pioneer Ellen White has written positively about Miller in The Great Controversy and elsewhere. She heard him preach, and accepted his teachings, going through the disappointment at age 16. She believed that his preaching fulfilled the prophecies of Scripture, and saw him being guided by the Lord.