Clayton's Guide, Clayton's Emigrant Guide, or as when published The Latter-Day Saints' Emigrants' Guide published by Missouri Republican Steam Power Press, Chambers & Knapp, 1848 and written by William Clayton, was one of a number of very popular guidebooks written to support the westward expansion of the United States in the mid-nineteenth century when organized emigrant wagon trains began to form in large numbers at various river ports on the Missouri River. — St. Louis: Mo. Republican Steam Power Press, Chambers & Knapp, 1848.