The “Monster” was an early four-axle locomotive with all wheels driven. The original locomotive was designed by Isaac Dripps and built in 1840 by the Camden & Amboy. The cylinders were situated in an inclined position above the second axle and acted on levers at the front of the locomotive. This power was transmitted to the third axle via connecting rods and the coupling rods only drove the fourth axle. The second axle was driven by the third one through a set of spur gears. Finally, a second set of coupling rods drove the first axle.

It was among the first, if not the first locomotive at all that was designed for burning anthracite. Its firebox had a combustion chamber and a water leg that created additional water circulation. In 1852 and 1853, long after the original locomotive had been built, two more each were built by the Trenton Locomotive Works. Some years later, Dripps rebuilt them to 4-6-0 locomotives. In this form, they were used until around 1875.