[Joseph Smith] Philadelphia, Pennsylvania. Although a small branch had been organized already in Philadelphia, Joseph Smith established a more extensive organization there. (1)
-- December 30, 1839
[Joseph Smith] Monmouth, New Jersey. Joseph Smith left Philadelphia and spent several days visiting a branch of the Church in New Jersey. (1)
-- 1839
[Membership] Church Membership at end of year: 16,460
New Converts : -1,421
Percent Change from previous year: -7.95% (2)
-- During 1839 Dec
[Lucy Mack Smith] Joseph visits Saints in Philadelphia and N.J. (3)
-- During 1839-41
[Brigham Young] Serves a mission to Great Britain. (4)
-- During 1839-1841
Robert Blashel Thompson -- primary scribal author for this period. Writings used in assembling The History of the Church (often cited as HC) (originally entitled History of Joseph Smith; first published under the title History of the Church of Jesus Christ of Latter-day Saints; nicknamed Documentary History of the Church or DHC) (5)
-- During 1839-1846
[Periodicals] Times and Seasons; E. Robinson and Don Carlos Smith Commerce Illinois (Nauvoo) (Periodical) (6)
-- 1840 January 11
[Wilford Woodruff] Arrives in Liverpool, England (7)
-- January 20, 1840
[Joseph Smith] Chester County, Pennsylvania. Joseph Smith wrote a letter to his wife, Emma Smith. (1)
-- 21 Jan. 1840
[Lucy Mack Smith] Martha Jane Knowlton receives her patriarchal blessing at Nauvoo from Joseph Smith Sr., in Lucy's presence. (8)
-- January 22, 1840
[Joseph Smith] Brandywine, Pennsylvania. In response to false rumors, Joseph Smith wrote a letter to the editor of the Chester County Register and Examiner relating the Churchs beliefs concerning civil governments. (1)
-- During Jan. 1840
[Lucy Mack Smith] Martha Jane Knowlton, a Campbellite, becomes the first member of her family to be baptized Mormon, John E. Page officiating. (8)
-- February 5, 1840
[Joseph Smith] Washington, D.C. Joseph Smith gave a public sermon on Latter-day Saint beliefs to an audience that included several members of Congress. (1)
Footnotes:
1 - BYU Studies Journal, volume 46, no. 4: A Chronology of the Life of Joseph Smith
2 - http://en.wikipedia.org/wiki/The_Church_of_Jesus_Christ_of_Latter-day_Saints_membership_history
3 - History of Joseph Smith by His Mother: Revised and Enhanced by Scot Facer Proctor Maurine Jensen Proctor
4 - Teachings of Presidents of the Church: Brigham Young, The Church of Jesus Christ of Latter-day Saints, Salt Lake City, Utah
5 - http://en.wikipedia.org/wiki/History_of_the_Church
6 - Encyclopedia of Mormonism, Vol.4, Appendix 3: Church Periodicals
7 - Wilford Woodruff's Journals 1833-1898: Typescript Edited by Scott G. Kenney, Signature Books, Midvale, Utah. Chronology
8 - Lucy's Book: A Critical Edition of Lucy Mack Smith's Family Memoir, Edited by Lavina Fielding Anderson, 2001, Signature Books
Mormon History Timeline /Chronology
http://lds-church-history.blogspot.com/
