Clayton's Guide,[1] Clayton's Emigrant Guide,[2] or as when published, The Latter-Day Saints' Emigrants' Guide,[2] published by Missouri Republican Steam Power Press, Chambers & Knapp, 1848[2] 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.