William McLellin, in a letter to D. H. Bays, writes that he left the Church in August 1836.
William E. McLellin, letter to D. H. Bays, November 23, 1869, repr. True Latter Day Saints’ Herald 17, no. 10 (May 15, 1870): 291
I remained with the church until August 1836, although sometimes much tried because of the conduct of her leading authorities. But when I saw them go into drunkenness and into ruinous speculation, pride and folly, I peaceably withdrew from them; merely writing back to them "it was because I had lost confidence in the HEADS of the church." I have never operated with Joseph Smith or his party from that day to this!!