This chapter examines Wharton’s writings on architecture and design, notably The Decoration of Houses (1897) and Italian Villas and Their Gardens (1904). Insisting on viewing house decoration as a branch of architecture, Wharton’s work in this field is not entirely original, but its scholarship and authority would elevate American public discourse on interior design and architecture to another level. At the end of the nineteenth century, and beginning of the twentieth, much of Wharton’s professional work was rooted in collaboration, bringing the author both frustrations and rewards. Architecture and design are shown as fields in which Wharton increasingly stepped away from theory in favour of practice, her early work at The Mount followed by the design of two internationally renowned gardens in France.