Just as the Rudo Ensayo is more an historic document than a mere history, so this new translation of it is more a documented interpretation than simply a new translation. The translator/editors bring their expert knowledge of the area, the language, and the history to every page of Nentvig's manuscript. Pradeau and Rasmussen have clarified many of the ambiguities of earlier translations by Smith (1863) and Guiteras (1894), and have added substantial annotations to the author's accounts of fauna and flora, native culture, and Spanish outposts. An incomparable record of a twelve-year mission in 18th century Sonora, the Rudo Ensayo as rendered in modern English is also a fascinating travelogue through an untamed land.

Dr. Alberto Pradeau's interest in the territory ceded to the United States by the treaty of Guadalupe Hidalgo February 2, 1848, began in 1908 with the reading of Samuel Woodworth Cozzens' book The Ancient Cibola: The Marvellous Country. Since 1940 this interest has been a relentlessly pursued hobby, and the present version of Rudo Ensayo is the result of personal knowledge, firsthand experience, and extensive research. Dr. Pradeau is a dental surgeon born in Sonora, Mexico, where he received his early education, and is a graduate of the University of Southern California.

Robert R. Rasmussen earned a bachelor's degree and a master's degree from California State University at Los Angeles in English literature. Having read the life of Father Eusebio Kino and become interested in the Catholic experience in New Spain during the seventeenth and eighteenth centuries, he worked very closely with Dr. Pradeau for several years in the preparation of this volume.