https://history.lds.org/article/samuel-smith-missionary-to-prophets?lang=eng
15 June 2016
Samuel H. Smith, though not as well known as his older brothers Joseph and Hyrum Smith, played an influential role in the early history of The Church of Jesus Christ of Latter-day Saints. In 1829 he moved to Harmony, Pennsylvania, to work Joseph’s farm while Joseph translated the Book of Mormon,
and he even briefly served as Joseph’s scribe. He was the third person baptized after the Aaronic Priesthood was restored, and he was chosen as one of the Eight Witnesses to see and handle the plates from which the Book of Mormon was translated. When the Church was organized, Samuel was one of the six original members. It seems fitting, then, that Samuel was called as the first missionary of the newly organized Church.