SC Johnson and the Johnson Foundation have added Herbert F. Johnson's home, Wingspread to its tour options. They have also expanded the tour season through December (handy if, say, you joined a political campaign and have hardly seen your wife and child since mid-August, and likely won't see them again until the first Wednesday in November).
Wright designed Wingspread for Herbert Johnson in the late 1930s, at the same time he designed SC Johnson's corporate headquarters in nearby Racine. The house is grand (14,000 square feet) with a careful mix of elegant public areas and intimate family space. Wright was extordinarily prod of the house and its high level of workmanship -- he even refered to it as the last Prairie House.
Until this announcement, tours of Wingspread were sharply limited. As the home of the Johnson Foundation, it's used as a confrence and educational center it was not open on a regular schedule.
Wingspread joins the SC Johnson Research Tower as the newest additions to the tour options of SC Johnson's campus. The tours are free. Here is the link for more information and to book your tour.
For more information about Wingspread, AD Classics has a nice entry on the house, and the Johnson Foundation has a small collection of images of original renderings, plans and photo of Wright and the modle of house.