Faced with the decision of whether to employ the promising, but new and uncertain technology of the steam locomotive, or to use stationary engines hauling trains via cable, and the decision of whose locomotives to use if any, the directors of the Liverpool and Manchester Railway, the world's first long distance passenger carrying rail line, decided to hold a public competition to find the most capable locomotive. The now famous Rainhill Trials were held on a newly-completed stretch of line near the town of that name in October 1829.

A sum of £500 was offered to the builder of the best locomotive that could meet these requirements:

  • Weigh less than six tons.
  • Not exceed 50 pounds per square inch of boiler pressure.
  • Capable of pulling at least three times its own weight on level ground at a speed of at least 10 miles per hour
  • The engine and boiler should be supported on at least six sprung wheels
  • The height including chimney should not exceed 15 feet
  • The engine should "effectively consume its own smoke" (A requirement pretty much ignored by all contestants, but it was a legal requirement)
  • There should be two safety valves on the boiler, one of which should be out of the reach of the engine-man's interference.

Although at least ten entrants attempted to build locomotives to enter in the Trials, in the end only five were ready in time. They were:

  1. Novelty, built by Braithwaite & Ericsson
  2. Sans Pareil, built by Timothy Hackworth
  3. Rocket, built by George and Robert Stephenson
  4. Cycloped, built by a Mr. Brandreth
  5. Perseverance, built by a Mr. Burstall

The Cycloped was powered by a horse on a treadmill, and was quickly eliminated, while the Perseverance was badly damaged in transit and was unable to take part.

Timothy Hackworth's Sans Pareil was judged to be overweight, but was permitted to take part anyway. All three locomotives proved to be quite able performers, but the Rocket had the edge even before its two competitors were forced to bow out due to mechanical failure; feed pump failure in the case of the Sans Pareil, and leaking boiler tube seals in the case of the Novelty.

The Rocket was judged to be the winner, through superior mechanical reliability as much as performance, though both it and the Sans Pareil were bought by the railway.