Orson Pratt Sr. (September 19, 1811 – October 3, 1881) was an American mathematician and religious leader who was an original member of the Quorum of the Twelve Apostles of the Church of Christ (Latter Day Saints). He became a member of the Quorum of the Twelve of the Church of Jesus Christ of Latter-day Saints (LDS Church) and was a leading Mormon theologian and writer until his death. Church membership and service Pratt was born in Hartford, New York, the son of Jared Pratt and Charity Dickenson. He was the younger brother of Parley P. Pratt, who introduced him to the LDS Church and baptized him on Orson's nineteenth birthday, September 19, 1830, in Canaan, New York. Pratt was ordained an Elder several months later, on December 1, 1830, by Joseph Smith and immediately set out for Colesville, New York, his first mission. This was the first of a number of short missions in which Pratt visited New York, Ohio, Missouri, and the Eastern States. On February 2, 1832, he was ordained a High Priest by Sidney Rigdon, then he continued his missions, preaching in Pennsylvania, New York, New Jersey, Vermont, New Hampshire, Connecticut, and Massachusetts. Pratt was a member of the original Quorum of the Twelve Apostles, called in 1835 under the direction of Joseph Smith. He was ordained to this position on April 26, 1835. He served as a member of the mission of the Twelve Apostles to the British Isles between 1839 and 1841. He contributed to the mission by preaching in Scotland, and producing an early missionary tract, "An Interesting Account of Several Remarkable Visions and the Late Discovery of Ancient American Records." This tract contains the earliest known public printing of an account of Smith's First Vision and also contains material similar to that later published as the 1842 Articles of Faith. On his return to America in 1841, Pratt found the church membership in contention over several issues. Rumors and gossip were rife in Nauvoo, Illinois, and Pratt found the religious principle of plural marriage difficult to accept. He rebelled against Joseph Smith when a report by disaffected Mormon John C. Bennett accused Smith of proposing marriage to Pratt's wife, Sarah Pratt, which Smith denied. Sarah also claimed that Smith had proposed, and Pratt believed his wife. After days of Smith and the other members of the Twelve remonstrating with Pratt, they decided