Messages that moved at the speed of people
For most of history, a message could travel no faster than the person, animal or ship carrying it. A letter from London to New York took weeks by sailing ship. A rider could cover a few dozen miles in a day, and relays of fresh horses could do better but at great expense. Even the best organized postal systems were limited by the roads and the weather.
Signaling systems offered some relief. Beacon fires, flags and towers could pass a short, pre-agreed message much faster than a rider, but they were limited by darkness, fog and distance, and they carried very little information. Their story is told separately under the optical telegraph; the point here is that none of them could carry an ordinary private message over a long distance.
What changed in the 1830s and 1840s
Several inventors in Britain, Germany, Russia and the United States produced working electric telegraphs in the 1830s. The British pair of William Cooke and Charles Wheatstone patented a system in 1837, and in the United States Samuel Morse and his collaborators, notably Alfred Vail, developed another around the same time. Credit is shared and sometimes disputed, but the principle was common: a current switched on and off at one end of a wire produced a signal that could be read at the other end.
The new element was not just speed but independence from the carrier. A message no longer had to travel with a person. As soon as it was sent, it was, for practical purposes, received. In 1844 a line between Washington and Baltimore carried Morse’s now-famous demonstration message, and commercial lines spread quickly afterward.
News
Newspapers were among the first big customers. Editors had always relied on mail, ships and local gossip for distant news, and reports could be days or weeks old. With telegraph lines, accounts of elections, battles and market moves could reach a newsroom the same day.
Cost was a problem, because each word was paid for. In 1846 several New York papers agreed to share the expense of telegraphed reports, an arrangement that grew into the Associated Press. In Europe, news agencies such as Reuters grew by selling telegraphed items to many papers at once. Writing became terser as a result: the compressed style of a wire report helped shape the modern news story, with the key facts first and detail afterward.
Business and markets
Merchants and bankers could compare prices in different cities within minutes. This narrowed the gaps that traders had once exploited between one market and another, and made it easier to manage distant branches. Orders for goods could be placed and confirmed quickly, which allowed firms to carry less stock.
At the same time, the early telegraph was expensive enough that ordinary people used it mainly for urgent messages, such as a death in the family or a business emergency. Ordinary correspondence stayed with the post for many years.
Railways
The telegraph and the railway grew up together. Early railways often ran on a single line, and avoiding collisions meant knowing where each train was. A telegraph line along the track let stations tell one another when a train had passed. Dispatchers could then give orders to trains by wire. One early use of telegraphed train orders in the United States is usually dated to the early 1850s on the Erie Railway. The approach spread widely and became standard practice on busy railroads, working hand in hand with railway signals.
Railways also provided the telegraph with a convenient right of way, and station staff often doubled as telegraph operators. The two networks reinforced each other as they expanded.
Limits and side effects
The telegraph did not work everywhere. Lines were vulnerable to storms, and breaks could stop a whole route. Long distances needed repeaters, devices that retransmitted a signal, or operators who copied and resent messages by hand. Messages also could not be entirely private, since operators read them, and companies developed codes and ciphers to save money and to protect secrets.
Operators themselves became a new occupation, with their own skills, speed contests and subculture. Many later turned to railroad or business careers.
A step toward everything that followed
By the 1860s, telegraph networks covered much of Europe and North America and had begun to cross water. The idea that a message could be separate from a messenger paved the way for later systems, including the telephone and wireless telegraphy, and in a broad sense for the later history of the internet. It also changed expectations: once people knew news could arrive the same day, waiting for weeks began to seem like a problem rather than a fact of life.