It was in the mid-1930's that Edgar J. Kaufmann, a Pittsburgh department store owner, commissioned Frank Lloyd Wright to design a year-round home for his mountain property in the Bear Run Valley of southwestern Pennsylvania, in a region known today as the Laurel Highlands. The key to the setting was the waterfall which had been a focal point for the Kaufmann family's activities. Wright envisioned the house as a series of horizontal concrete trays with upturned stiffening edges, trays that were spaced one above the other by short vertical stone masses. A great central chimney was fixed atop a large boulder whose natural upper surface became the hearth in the living room. Around this point, Wright swung his spaces; the living room cantilevered southward over the falls; to the east were the entrance areas, to the west the kitchen, and to the north a narrow strip for stairs and dining. The structural engineers who consulted on the job had misgivings about architecture that made structural use of parapets at the edges of concrete slabs, rather than regarding them as dead weights. Kaufmann was assured that the house could not stand up. Over the next few months there was a perceptible natural settlement of the cantilevers. The dire predictions of the engineers had so unnerved the owner that for several years he had levels sighted regularly on the extreme points. Finally they learned that the building was in continual motion, imperceptible to the naked eye, expanding and contracting; a survey point that fell a fraction of an inch one year might rise as much or more the next. Misgivings of the Kaufmann family as to the structural integrity of the house were stilled at last by a freak storm when the entire house was engulfed in a sudden torrential flood. Damage to surrounding property was enormous, but the house stood firm and undamaged; only the mud and sand had to be cleaned away. Few houses could have withstood such a test.