March 18, 1833 – Sidney Rigdon and Frederick G. Williams were appointed and set apart by President Joseph Smith to be his Counselors in the Presidency of the Church, according to the revelation given March 8th. On the same occasion “many of the brethren saw a heavenly vision of the Savior and concourses of angels.”
March 20, 1839 – Joseph Smith, jun., who was still imprisoned in Liberty jail, Mo., wrote an excellent epistle “to the Saints at Quincy, Ill., and scattered abroad,” in which was embodied a most fervent prayer in behalf of the suffering Saints, and words of prophecy. (See Doc. and Cov., Sec. 121, and History of Joseph Smith.)
March 20, 1842 – The Prophet Joseph Smith baptized 80 people in the Mississippi River near his home, including M.L.D. Wasson, a nephew of Emma Smith, the first of her family to join the Church.
March 18, 1843 – The Prophet Joseph spent the morning in his office working. He records, “About noon, I lay down on the writing table, with my head on a pile of law books, saying, ‘Write and tell the world I acknowledge myself a very great lawyer; I am going to study law, and this is the way I study it;’ and then fell asleep.”
March 18, 1962 – The first stake in Western Samoa is organized in Apia.
Taken from: History of Joseph Smith 1:335; 5:306; and Church Chronology by Andrew Jenson