In the 1830s a man, every business day, would climb to the top of the dome of the Merchant’s Exchange on Wall Street, where the New York Stock and Exchange Board then held its auctions. There he would signal the opening prices to a man in Jersey City, across the Hudson. That man would signal them in turn to a man at the next steeple or hill, and the prices could reach Philadelphia in about thirty minutes.
That is from John Steele Gordon’s excellent An Empire of Wealth: The Epic History of American Economic Power. Here is my previous post on the book.