What impacts did the telegraph have on society and the economy?
Wars could be ended, and stocks sold, around the world in something approaching real time.
Andrew Jackson was the breakout hero of the War of 1812, routing the British at the Battle of New Orleans. Sadly, a treaty had already ended the war several days earlier. Prior to 1858, the laying of the first Transatlantic Cable, it took ten days to get a message from London to New York, and it was carried on a ship.
It was not uncommon in the early 19th Century for an investor in England to own stock in an American company, or an American to own a piece of a British one. Stocks and bonds were bought and sold back then for much the same reasons they are today. The difference is, relevant information that could affect buy and sell orders was a week and a half old before an investor could act on it, and his decision would take another 10-12 days to take effect..
With the telegraph, these transactions took hours instead of weeks or months to complete and the information spurring these orders was still relatively fresh.
Today, of course, these orders can take effect in a fraction of a second. But going from twenty days to under two hours was quite a leap of progress.