The “Pennsylvania” of the Philadelphia & Reading wasn't only the biggest of the camelbacks designed by James Milhlolland, but also the biggest locomotive in the world when it was completed in 1863. It was a 0-12-0 that was used as pusher on the steep Falls Grade near Philadelphia, Pennsylvania.
A special feature of this locomotive was that it didn't have a separate tender, but wasn't a real tank locomotive either. This meant that it had no coal bunker and only small water tanks, but was stoked before each of the short climbs. Since it was found out that the freight cars of the time couldn't handle the forces of this massive locomotive, it was rebuilt in 1870. It now had only five axles, a tender and a new cab. 