Sidney Rigdon
Sidney Rigdon was born in 1793 near St. Clair Township, Pennsylvania. He was the son of a farmer, who did not want Sidney to become a preacher. However, Sidney eventually made the acquaintance of Alexander Campbell, leader of the Campbellite movement, a subset of the Reformed Baptist Movement. (Campbell’s group later became the Disciples of Christ.) Rigdon eventually established a congregation in Ohio. He was known as a great orator, and held many religious debates with ministers in the surrounding area.
Conversion
Parley P Pratt learned of the Book of Mormon on a boat stop on the Erie Canal. His conversion on Sept 1, 1830 is well-documented in the movie, How Rare a Possession, put out by the church. Pratt was hopeful that Rigdon would receive that message, and arrived with Oliver Cowdery. Sidney was at first quite skeptical of the Book of Mormon, and is said to have thrown the book down and said it was fiction. However, he kept reading, and eventually joined the LDS church in November or December 1830.
He announced his conversion to the congregation he administered, and as many as 100 people converted with him. However, as a result of his conversion, the congregation evicted him from the partially completed home owned by the congregation.
LDS Leadership
Rigdon finally met Smith in Dec 1830, and the two became fast friends. Rigdon soon became a counselor in the First Presidency, and was Joseph Smith's Vice Presidential candidate in 1844, just before Joseph was killed.
Life After Martyrdom
Rigdon felt inspired to lead teh church after the death of the prophet. While there was much debate about who would lead teh church in the aftermath of Joseph's death, Brigham Young took over leadership of the church. Rigdon was excommunicated by Young, and returned to Pennsylvania, and established his own brand of Mormonism, called the Church of Jesus Christ of the Children of Zion, also known as the Rigdonites. The church faltered, and eventually was observed by William Bickerton's group (the Bickertonites), which still revere Rigdon.