George Stephenson is said to have produced sixteen locomotives altogether at Killingworth, although it has never proved possible to produce a convincing list of all sixteen.

Of those that have been identified most were built for use at Killingworth itself or for the Hetton colliery railway.

A six-wheeled locomotive had been built for the Kilmarnock and Troon Railway in 1817 but it was soon withdrawn from service because of damage to the cast iron rails.

A further locomotive had been supplied to Scott's Pit railroad at Llansamlet, near Swansea in 1819 but it too was soon withdrawn, apparently because it was under-boilered and also because of damage to the track.

The new engines are too heavy to be run on wooden rails, and iron rails are in their infancy, with cast iron exhibiting excessive brittleness.

Together with William Losh, Stephenson has improved the design of cast iron rails to reduce breakage; these are briefly made by Losh, Wilson and Bell at their Walker ironworks.

According to Rolt, Stephenson had also managed to solve the problem caused by the weight of the engine upon these primitive rails.

He had experimented with a 'steam spring' (to 'cushion' the weight using steam pressure), but soon followed the new practice of 'distributing' weight by utilizing a number of wheels.

For the Stockton and Darlington Railway, however, Stephenson will use only wrought iron rails, notwithstanding the financial loss he will suffer from not using his own, patented design. (Nock, Oswald (1955). "Building the first main lines". The Railway Engineers. London: Batsford. p. 62.)

Stephenson had been hired to build an eight-mile (thirteen kilometer) railway from Hetton colliery to Sunderland in 1820.

The finished result uses a combination of gravity on downward inclines and locomotives for level and upward stretches.

It is the first railway using no animal power.

The world's first modern railway, the Stockton and Darlington Railway, opens in England on September 27, 1825.

A parliamentary bill had been passed in 1821 to allow the building of the Stockton and Darlington Railway (S&DR).

The twenty-five-mile (forty kilometer) railway is intended to connect various collieries situated near Bishop Auckland to the River Tees at Stockton, passing through Darlington on the way.

The original plan was to use horses to draw coal carts on metal rails, but after company director Edward Pease met Stephenson he had agreed to change the plans.

George Stephenson surveyed the line in 1821, assisted by his eighteen-year-old son Robert.

Construction of the line began the same year.

A manufacturer was now needed to provide the locomotives for the new line.

As it turned out, Pease and Stephenson jointly established a company in Newcastle to manufacture locomotives.

The company was set up as Robert Stephenson and Company, and George's son Robert was the managing director.

A fourth partner is Michael Longridge of Bedlington Ironworks.

An early trade card describes Robert Stephenson & Co as "Engineers, Millwrights & Machinists, Brass & Iron Founders".

In September 1825, the works at Forth Street, Newcastle complete the first locomotive for the new railway: originally named Active, it is soon renamed Locomotion.

It will be followed by Hope, Diligence, and Black Diamond.

Locomotion, driven by Stephenson, haul an eighty-ton load of coal and flour nine miles (fifteen kilometers) in two hours, reaching a speed of twenty-four miles per hour (thirty-nine kilometers per hour) on one stretch.

The first purpose-built passenger car, dubbed Experiment, is attached, and carries dignitaries on the opening journey.

It is the first time passenger traffic has been run on a steam locomotive railway, representing a revolution in land transportation.

The rails used for the new line are wrought-iron ones, produced by John Birkinshaw at the Bedlington Ironworks.

Wrought-iron rails can be produced in much longer lengths than the cast-iron ones and are much less liable to crack under the weight of heavy locomotives.

William Losh of Walker Ironworks had thought that he had an agreement with Stephenson to use his cast-iron rails, and Stephenson's decision causes a permanent rift between the two men.

The gauge that Stephenson has chosen for the line is 4 feet 8½ inches (1,435 millimeters), and this will subsequently come to be adopted as the standard gauge for railways, not only in Britain, but also throughout the world.

Stephenson moves to the Liverpool and Manchester Railway the same year.

A competition to decide whether stationary steam engines or locomotives will be used to pull the trains has been arranged by the directors of the Liverpool and Manchester Railway as it approaches completion.

The Rainhill Trials, held in October of 1829 in Rainhill, Merseyside (between Liverpool and Manchester) are arranged as an open contest that will let them see all the locomotive candidates in action, with the choice to follow.

Regardless of whether or not locomotives were settled upon, a prize of five hundred pounds is offered to the winner of the trials.

Swedish inventor and mechanical engineer John Ericsson, while surveying in northern Sweden as an army lieutenant, had in his spare time constructed a heat engine that used the fumes from the fire instead of steam as a propellant.

His skill and interest in mechanics made him resign from the army and move to England in 1826.

However, his heat engine was no success, as his prototype was designed to use birch wood as fuel and would not work well with coal, which was the main fuel used in England.

Notwithstanding the disappointment, he invented several other mechanisms instead based on steam, improving the heating process by adding fans to increase oxygen supply to the fire bed.

In 1829, his steam engine "Novelty" joins the Rainhill Trials, in which ten locomotives are entered, but on the day the competition begins—October 6, 1829—only five locomotives actually begin the tests.

Although "Novelty" is the fastest in the competition, it suffers recurring boiler problems and cannot continue to compete—the competition being won by the English engineer George Stephenson and his son Robert, who, having built the “Rocket” after three years of work, receive the five hundred pound prize.

U. S. railways will soon begin importing English locomotives.

The Liverpool and Manchester Railway, the world's first intercity passenger railway operated solely by steam locomotives, opens on September 15, 1830, using steam power for both freight and passenger and service.