The 35-room, 12,000-square-foot mansion Wright designed for Susan Lawrence Dana is a sophisticated integration of architecture, furnishings and decorative arts, a complete and unified statement of the Prairie School aesthetic and the largest example of Wright’s Prairie-period houses to survive. His double cross-axis plan incorporated vestiges of the family’s original 1868 home in the foundation, walls and fireplace. The gable roof and unusual flaring copper gutters lend an Asian character to the building. More than 450 pieces of art glass, including 200 light fixtures, and more than 100 pieces of oak furniture were designed and produced for the site, which was acquired by the State of Illinois in 1981.