When the original Planet was built in 1830 it was the ninth locomotive to be built for the Liverpool & Manchester Railway. It was built by Robert Stephenson who had built Rocket but was a major advance on the earlier design. It was the first locomotive to have inside cylinders.
In November 1830 the locomotive covered the 30 miles between Liverpool and Manchester in one hour.
Six more locomotives of this design were ordered by the railway from Robert Stephenson & Co and a further three from Murray & Wood in Leeds. The latter three were based on drawings provided by Robert Stephenson & Co.
In 1992 a working replica was built by Friends of the Museum of Science and Industry in Manchester.