The completion of this work serves to impress the writer with the many problems in New Mexico history which are, as yet, untouched. The recent publication of archival studies, such as those of the Quivira Society, is a challenge to scholars to utilize these sources for the production of specific studies in the social, economic, religious, and political phases of New Mexico history.<br><br>Four centuries of history under Spain, Mexico, and the United States have produced a multitude of cultural developments which must, necessarily, be investigated before a thorough history of New Mexico can be written. No more vital influence on the development of the Spanish Southwest can be distinguished than that played by the exploration, settlement, granting, and use of the land making up this vast area. The present study is to serve as an introduction to the investigation of the complex Spanish and Mexican land grant problem in New Mexico and the Southwest. A second volume dealing with the Pueblo Indian Land Grants of the "Rio Arriba," New Mexico, is in preparation. The history of the private land grants is a natural consequence of this study. Investigation in this field is progressing rapidly.<br><br>To Mark C. Radcliffe, of the Department of the Interior, and to Mr. Guy Harrington, Cadastral Engineer for New Mexico, the writer expresses his appreciation for the many courtesies extended during the preparation of this study. Appreciation for her assistance is due Doctor Dorothy Woodward, of the University of New Mexico. The gratitude which the author owes Dean George P.Hammond for his advice, guidance, and aid, is inexpressible. The worth of this study, if such there be, must be credited to those mentioned above who have given of their time and energies so willingly. For the shortcomings and errors the writer accepts complete responsibility.