During the summer of 1941 the writer made a survey of the sites in Canyon de Chelly National Monument, Arizona, which represent the later phases of Modified Basket Maker and the early phases of the Developmental Pueblo period. The object of this survey was to trace the development of architecture from the early slab-lined pit houses to the above-ground dwellings constructed of linearly-laid stone masonry. Since the writer lacked the facilities for any intensive excavations, the information contained in the paper was on the whole based on surface observation.