The “Locomotion” was the first locomotive to transport paying passengers. Orders for them and a second locomotive came from the Stockton and Darlington Railway on 16 September, 1824 at a cost of £550 each. George Stephenson and his son Robert had already gained experience in building the so-called Killingworth locomotives, which were used in the mine of the same name. Based on these locomotives, number 1, which was initially called “Active”, was delivered in September 1825. On September 26, it ran under its own power for the first time as a test, and the route was officially opened the following day. In order to prove their efficiency, the inaugural run was completed with a load of eleven coal wagons, the first real passenger wagon called “Experiment” and 20 other wagons with passengers. Even with this 120 meter long train weighing about 80 tons, a speed of 12 mph could be reached.

The locomotive itself was apparently no more than a wood-lined boiler on wheels, complete with a chimney and connecting rods. The crew stood on the towed tender. The two cylinders were placed inside the boiler to prevent the steam from condensing. For the first time ever, the axles were connected via coupling rods, which prevented the wheels from slipping. Only a single flame tube served as a heating surface, but the locomotive already had an induced draft to fan the fire with the exhaust steam from the cylinders. After three years in service, the “Locomotion” suffered a boiler explosion due to human error, which claimed the life of the driver. After reconstruction, it was quickly overshadowed by newer locomotives and was used until about 1850. It was still used as a stationary steam engine until 1857, and then it was the first locomotive ever to be preserved as a functioning museum piece. In the years that followed, it made several special trips, the last of which was in 1881. It has been on display in Darlington since 1892, where it changed locations several times.