Examples of sorghum's antique technology can be seen at Cades Cove, an open-air museum in the Great Smokey Mountains National Park, where the Guenthers keep a pair of draft horses hitched to their original mill for demonstration purposes. Today, however, they rely on machinery scaled to their annual production of some 9,000 gallons, harvesting and crushing their 60 acres of sorghum in the field, with a tractor-drawn contraption assembled from a corn harvester, a concrete mixer and a thousand-gallon tank. Inside the cooking shed, clouds of vapor rise from a steam-heated pan the size of a swimming pool; a labyrinth of metal fins channel the hot syrup back and forth as it runs down the pan’s gentle incline. When it reaches the bottom, the syrup is sparkling brown and clings to a chilled spoon. The Houston family’s sorghum, by contrast, is nearly black and, on a cool day, solid enough to sit on the tines of a fork.