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By 1844, the Morse system connected Baltimore to Washington, and by 1861 the west coast of the continent was connected to the east coast. As late as 1844, after the electrical telegraph had come into use, the Admiralty's optical telegraph was still used, although it was accepted that poor weather ruled it out on many days of the year. The first commercial telegraph was by Cooke and Wheatstone following their English patent of 10 June 1837. It was demonstrated on the London and Birmingham Railway in July of the same year. This was the system that first used the soon-to-become-ubiquitous Morse code. The Morse system was officially adopted as the standard for continental European telegraphy in 1851 with a revised code, which later became the basis of International Morse Code. Likewise, the United States continued to use American Morse code internally, requiring translation operators skilled in both codes for international messages.

Cooke extended the line at his own expense and agreed that the railway could have free use of it in exchange for the right to open it up to the public. However, this led to a breakthrough for the electric telegraph, as up to this point the Great Western had insisted on exclusive use and refused Cooke permission to open public telegraph offices. The world's first permanent railway telegraph was completed in July 1839 between London Paddington and West Drayton on the Great Western Railway with an electric telegraph using a four-needle system. The first operative electric telegraph (Gauss and Weber, 1833) connected Göttingen Observatory to the Institute of Physics about 1 km away during experimental investigations of the geomagnetic field. On 12 June 1837 Cooke and Wheatstone were awarded a patent for an electric telegraph. In Cooke's original system, a single-needle telegraph was adapted to indicate just two messages: "Line Clear" and "Line Blocked". The present complete system, as used between Liverpool and Manchester, was constructed as follows: Iron or stoneware pipes were laid from one to two feet below the level of the road-side with flush-boxes coming to the surface every two hundred yards.

Next morning this pioneer line was broken down at a point about 200 Yards from Cape Grisnez, and it turned out that a Boulogne fisherman had raised it on his trawl and cut a piece away, thinking he had found a rare species of tangle with gold in its heart. Gold is also used in applications because it is corrosion resistant. Entry to and exit from the block was to be authorised by electric telegraph and signalled by the line-side semaphore signals, so that only a single train could occupy the rails. The Morse system uses a single wire between offices. The temperature rating of a wire or cable is generally the maximum safe ambient temperature that the wire can carry full-load power without the cable insulation melting, oxidizing, or self-igniting. Wigwag achieved this by using a large flag-a single flag can be held with both hands unlike flag semaphore which has a flag in each hand-and using motions rather than positions as its symbols since motions are more easily seen. The concept of a signalling "block" system was proposed by Cooke in 1842. Railway signal telegraphy did not change in essence from Cooke's initial concept for more than a century.

It was used to manage railway traffic and to prevent accidents as part of the railway signalling system. However, in trying to get railway companies to take up his telegraph more widely for railway signalling, Cooke was rejected several times in favour of the more familiar, but shorter range, steam-powered pneumatic signalling. 16,37 France had an extensive optical telegraph system dating from Napoleonic times and was even slower to take up electrical systems. The Prussian system was put into effect in the 1830s. However, what is electric cable they were highly dependent on good weather and daylight to work and even then could accommodate only about two words per minute. Even when his telegraph was taken up, it was considered experimental and the company backed out of a plan to finance extending the telegraph line out to Slough. Miles had previously set up the first heliograph line in the US between Fort Keogh and Fort Custer in Montana. The idea for a telegraph of this type was first proposed as a modification of surveying equipment (Gauss, 1821). Various uses of mirrors were made for communication in the following years, mostly for military purposes, but the first device to become widely used was a heliograph with a moveable mirror (Mance, 1869). The system was used by the French during the 1870-71 siege of Paris, with night-time signalling using kerosene lamps as the source of light.

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