First a trapper and trader, then a merchant, and finally an emerging capitalist in the flour industry of New Mexico and Colorado, Ceran St. Vrain was an iconic image of the industrious and self-reliant western pioneer of the 19th century. He was also a military hero, aiding the U.S. dragoons as an officer in the New Mexico Volunteer army in their fight against marauding plains Indians alongside Kit Carson. An intelligent and affable soul, he helped lead the southwest from a barter economy, poor in cash and lacking political infrastructure, into a post-military commercial society on the road to statehood. His name has long been associated with a small handful of astute and skilled leaders in the transformation of the southwest: Carson, the Bent brothers, Charlies Beaubien, Lucien Maxwell, Colonels Sterling Price and E.V. Sumner, and yet until now his story has been largely hidden in footnotes and brief accounts of particular exploits. This story of St. Vrain was stimulated by the author's earlier excavation of his first flour mill in Taos, and the need to make that excavation record public. Hence, this volume is in two parts: Part I is a biographical account of St. Vrain's life from his entry into New Mexico in the 1820s until his death in 1870. Part II is a detailed description of the mill excavations and interpretations.