The sources of the history of the Rio Grande Pueblos, both printed and in manuscript, are numerous. The manuscript documents are as yet but imperfectly known. Only that which remained at Santa Fe after the first period of Anglo-American occupancy--a number of church books and documents formerly scattered through the parishes of New Mexico, and a very few documents held in private hands--have been accessible within the United States. In Mexico the parish and other official documents at El Paso del Norte (Juarez) up to the beginning of the eighteenth century have been examined by me to a certain extent, and at the City of Mexico the Archivo Nacional has yielded a number of important papers, though the research has been far from exhaustive, owing to the lack of time and support. Hence much still remains to be done in that field. Some destruction of papers of an official character appears to have taken place at Mexico also, yet with the present condition of the archives there is hope that much that appears to be lost will eventually be brought to light; in any event we still have recourse to the Spanish archives, principally at Sevilla. It was the rule during Spanish colonial domination to have every document of any importance executed in triplicate, one copy to remain at the seat of local government, another to be sent to the viceregal archives, and the third to the mother country. Hence there is always a hope that, if the first two were destroyed, the third might be preserved. So, for instance, the collection of royal decrees (_cedulas_) is imperfect at the City of Mexico. There are lacunae of several decades, and it is perhaps significant that the same gaps are repeated in the publication of the "Cedulas" by Aguiar and Montemayor. In regard to ecclesiastical documents the difficulty is greater still. The archives of the Franciscan Order, to which the missions on the Rio Grande were assigned almost until the middle of the nineteenth century, have become scattered; the destruction of the archives at the great Franciscan convent in the City of Mexico in 1857, though not complete, resulted in the dispersion of those which were not burned or torn, and the whereabouts of these remnants are but imperfectly known. The documentary history of the Rio Grande Pueblos, therefore, can be only tentative at present, but it is given in the hope that it will incite further activity with the view of increasing and correcting the data thus far obtained. * * * * *