How has the study of the built environment changed the historiography of gender? This paper analyzes the shifts in the historiography of women and gender in late nineteenth- and early twentieth-century American history. It examines the evolution from a metaphorical concept of spheres to a more complex understanding of the interactions between space and gender. In the 1960s, feminist historians introduced the concept of ‘separate spheres’ as a way to understand the history of women in the nineteenth century. When historians, in the 1970s and 1980s, began to study actual spaces it became clear that the relationship of gender and space was more complex than the dichotomies of public and private, male and female, urban and suburban, which reinforced the idea of separate spheres. The study of actual spaces demonstrates that the boundaries of everyday life were more porous than those idealized by separate spheres and spaces. Further, scholars in the 1990s were able to show how the design, spatial arrangement, and décor of spaces contributed to the construction of masculinity and femininity in relation to each other.