This dissertation focuses on the nature of architectural space in the Caddo area of eastern Texas, in the southwestern portion of the Caddo archaeological area. The early European accounts and the archaeological record indicate there was a wide range in size, shape, form, and use of architectural space in the Caddo area. Buildings have a variety of structural attributes and may be found isolated or associated with plazas or earthen mounds. This dissertation is a detailed examination of this architectural diversity. The sites included in this study range from large multi-mound centers that have seen large-scale and long-term research, such as the George C. Davis site, to smaller hamlets and farmsteads. This study includes 265 structures from 31 sites located throughout the Pineywoods, Post Oak Savanna and Blackland Prairie of eastern Texas. This dissertation provides an examination of the structuring of architectural space by Caddo groups living in eastern Texas. Through a detailed examination of documentary, archaeological, and geophysical data, this research examines the nature of the Caddo built environment; how Caddo cultural space was created, maintained, and altered, and how this relates to broader Caddo society. The purpose of this dissertation is to provide descriptions and comparisons of Caddo architecture from eastern Texas to address three interrelated themes: cultural significance of architectural space to the Caddo, physical form of structures and construction attributes, and variation and change. / text