The Baltimore-Washington telegraph line was the first long-distance telegraph system set up to run overland in the United States.
Originally Morse decided to lay the wire underground, and he asked Ezra Cornell to lay the line using a special cable-laying plow that Cornell had developed. Wire began to be laid in Baltimore on October 21, 1843. Cornell's plow was pulled by eight mules, and cut a ditch 2 inches (5.1 cm) wide and 20 inches (51 cm) deep, laid a pipe with the wires, and reburied the pipe, in an integrated operation. But the project was stopped after about 15 kilometres (9.3 mi) of wire was laid because the line was failing. Morse learned that Cooke and Wheatstone in England were then using poles for their lines, and he decided to follow that lead.
Installation of the lines and poles from Washington to Baltimore began on April 1, 1844. Chestnut poles of 7 metres (23 ft) in height were used, placed 60 metres (200 ft) apart, using a total of about 500 poles. Two 16-gauge copper wires were installed; they were insulated with cotton thread, shellac, and a mixture of "beeswax, resin, linseed oil, and asphalt." A 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 sent 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.