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.

The Monkland and Kirkintilloch Railway opens in Scotland on October 1, 1826.

The City of Glasgow has a large and increasing requirement for coal, for domestic and industrial use,
in the first decades of the nineteenth century, and after the cessation of coal extraction from local pits, this is chiefly supplied from the Lanarkshire coal field, centered near Airdrie, in Monkland.

There is also some extraction of iron ore in the area.

The Monkland Canal had opened in 1794, and provided a considerable stimulus to the coalpits in Monkland, and early iron workings were encouraged also.

However, before the era of a proper road network, the canal had a virtual monopoly of transport, and it set its prices accordingly.

A group of interested businessmen had promoted the Monkland & Kirkintilloch Railway to link the coal pits and iron works to the Forth and Clyde Canal at Kirkintilloch.

If coal and minerals were transshipped there, they could reach not only Glasgow, escaping the monopoly of the Monkland Canal but also Edinburgh.

The scheme had obtained parliamentary authority on May 17, 1824, with share capital of £32,000 and powers to raise a further £10,000 by additional shares or by borrowing.

Construction started by contract the following month.

The engineer for the scheme was Thomas Grainger, in his first large undertaking; he had previously been chiefly engaged in road schemes.

When he became engaged on the construction of the railway, he took as his assistant John Miller, and a year later the two men formed a partnership, Grainger & Miller, which is to be heavily involved in Scottish railway schemes.

It is built to the track gauge of 4 ft 6 in (1,372 mm), and as other 'coal railways' open up in the area in connection with the line, this track gauge will become established for their use.

It is not known why Grainger chose this gauge.

He must have been aware of the huge success of the Stockton and Darlington Railway, built to a gauge of 4 ft 8½ in.

The convention for specifying gauge had not settled down at this early date, and it is not impossible that Grainger intended to imitate the Stockton line but mistook the parameter.

Whatever the reason, he inadvertently causes huge disadvantage to the M&KR and several other coal railways in Central Scotland.