The Baltimore-Washington telegraph line was the first long-distance telegraph system set up to run overland in the United States.
In March 1843, the United States Congress appropriated $30,000 to Samuel Morse in order to lay a telegraph line from Washington, D.C. to Baltimore, Maryland, along the right-of-way of the Baltimore and Ohio Railroad.
Originally Morse decided to lay the wire underground, and asked Ezra Cornell to lay the line using a special cable-laying plow that Cornell developed. Wire began to be laid in Baltimore on October 21, 1843. Cornell's plow was pulled by eight mules, and cut a ditch two inches wide and twenty inches deep, laid a pipe with the wires, and reburied the pipe, in an integrated operation. But the project was stopped after 15 km of wire was laid because the line was failing. Morse learned that Cooke and Wheatstone in England were now using poles for their lines, and he decided to follow that lead.
Work began in Washington on laying the line to Baltimore using poles on April 1, 1844. They used chestnut poles of seven meters in height, and 60 meters apart. Two wires were laid, Number 16 copper wire, covered by cotton thread with shellac, and a covering mixture of "beeswax, resin, linseed oil, and asphalt." An impressive test of the still incomplete line occurred on May 1, 1844, when news of the Whig Party's nomination of Henry Clay for U.S. President was telegraphed from the party's convention in Baltimore to the Capitol Building in Washington.
Morse's line was demonstrated on May 24, 1844, from the Old Supreme Court Chamber in the United States Capitol in Washington to the Mount Clare station of the railroad in Baltimore, and commenced with the transmission of Morse's first message (from Washington) to Alfred Vail (in Baltimore), "What hath God wrought?", a phrase from the Bible's Book of Numbers. The phrase was suggested by Annie Ellsworth, whose husband was a supporter of Morse's, and knew Morse was religious.
The next year, Johnson reported that "the importance of [the line] to the public does not consist of any probable income that can ever be derived from it," which led to the invention being returned for private development.