This essay examines the relationship between the period room and the American art museum during the first three decades of the twentieth century. The growing popularity of period rooms just after World War I reflected changing expectations about art, history, and the larger museum experience. The expansion of period rooms during the 1920s anticipates merchandising concepts that are now commonplaces of museological debates. After surveying early art museums as exhibition sites, I will examine the broader turn to context, detail social and museum-related factors in the rise of period rooms, and comment on their impact.