1863. THE PENNSYLVANIA
THE first engine to be built with six pairs of driving wheels was the Pennsylvania, designed by James Milholland and completed at the Philadelphia & Reading Shops in 1863. It was intended and used for pusher service, particularly in handling coal trains over the summit of the hills between the Schuylkill and Delaware Rivers.

Though originally both fuel and water were carried on the engine, when it was rebuilt in 1870, with the rear pair of drivers omitted, a separate tender was attached. The principal reason for its being modified was because it had difficulty in negotiating curves, some of which were as short as 320-foot radius. It was so powerful that it was destructive to the light cars then used for handling coal.

Cylinders 20 by 26 inches Weight 100,300 pounds Driving wheels 43 inches in diameter Wheelbase 19 feet 7 inches