From the National Archives:
When Lincoln arrived as President-elect in 1861, the nation’s leaders did not fully appreciate the relatively new technology of the telegraph. The famous words “What hath God wrought!” had been telegraphed from the Capitol building almost 17 years earlier. But to most people of the 1860s, the very idea of electricity—much less the notion of sending messages over distances by sparks of electricity—was only a vague scientific concept. Leaders remained flummoxed as to how the Federal Government could use the new technology. There was no telegraph station to the White House, or at the Navy Yard, or at the War Department. When the U.S. Army wanted to send a telegram, it handed the text to a clerk, who then stood in line at the central telegraph office.
To Abraham Lincoln, however, this new technology offered a capability unavailable to any other leader in history. Traditionally, leaders had traveled with their armies, like Henry V at Agincourt and Bonaparte in Russia. Lincoln now had the ability to communicate in real time with armies in the field from the political capital. But he had to figure out how to use the new technology to his greatest advantage–without the guidance of precedent, without a text to study, without a tutor’s guidance, and in the midst of the Civil War.
Fortunately, Lincoln was instinctively comfortable with new technology. He was the only President to hold a patent and had been involved with the spread of innovations such as the railroad in his native Illinois. He embraced the telegraph to interject his leadership from afar—and this was essential to winning the Civil War. [...]
Telegram from President Lincoln to Lt. General Grant encouraging him to hold on with a “bull dog grip,” August 17, 1864