A lightweight fiberglass powerboat called Fountain Lightning can top 142 mph on still water. That's a powerful boat. A tug now under construction in China will tow an entire offshore oil-drilling platform into place, even on a restless sea. That's also a powerful boat. When talk turns to machine muscle, it's often about the most powerful engine that will fit into and move a machine. But to build an authentic Power List you have to ask what the measure and purpose of the power is: horsepower, torque, acceleration, top speed, hauling capacity, lift. The short power profiles here focus almost exclusively on machines that are made (or at least assembled) in the United States. And no stunt machines, no machines built solely to demonstrate power, no school buses with jet turbines attached, were allowed. These machines do an honest day's work.