...Baltimore. The most convincing demonstration occurs when…
May 1844 CE
...Baltimore.
The most convincing demonstration occurs when the results of the Whig National Convention at Baltimore in the spring of 1844 reaches Washington via telegraph prior to the arrival of the first train.
The line (which runs along the Baltimore and Ohio Railroad between the Capitol and Baltimore) is officially opened on May 24, 1844, as Morse sends his famous words "What hath God wrought" along the wire to the railroad's "outer depot" in Baltimore, saying "What hath God wrought".