That message was sent by Samuel F.B. Morse, the inventor of Morse code and the electric telegraph on May 24, 1844, from Washington, DC, to Baltimore – and then sent back again by Morse’s assistant, Alfred Vail. What was the message?
“What Hath God Wrought”
By the way, the message is a biblical quotation from Numbers 23:23. The message was chosen for Morse by Annie Ellsworth, daughter of the Governor of Connecticut.