American Morse code

American Morse Code — also known as Railroad Morse—is the latter-day name for the original version of the Morse Code developed in the mid-1840s, by Samuel Morse and Alfred Vail for their electric telegraph. The "American" qualifier was added because, after most of the rest of the world adopted "International Morse Code," the companies that continued to use the original Morse Code were mainly located in the United States. American Morse is now nearly extinct—it is most frequently seen in American railroad museums and American Civil War reenactments—and "Morse Code" today virtually always means the International Morse which supplanted American Morse.

American Morse Code was first used on the Baltimore-Washington telegraph line, a telegraph line constructed between Baltimore, Maryland, and the old Supreme Court chamber in the Capitol building in Washington, D.C. The first public message "" was sent on May 24, 1844, by Morse in Washington to Alfred Vail at the Baltimore and Ohio Railroad (B&O) "outer depot" (now the B&O Railroad Museum) in Baltimore. The message is a Bible verse from Numbers 23:23, chosen for Morse by Annie Ellsworth, daughter of the Governor of Connecticut. The original paper tape received by Vail in Baltimore is on display in the Library of Congress in Washington, D.C.

In its original implementation, the Morse Code specification included the following:

Various other companies and countries soon developed their own variations of the original Morse Code. Of special importance was one standard, originally created in Germany by Friedrich Clemens Gerke in 1848, which was simpler—it eliminated the long intra-character spaces and the two long dashes—but also included changes in the sequences for eleven of the letters and most of the numerals. The Gerke code had a distinct advantage for use on undersea telegraph cables. Cables suffer from a type of distortion called dispersion that gets progressively worse with the length of the cable. Dispersion severely limits the rate that Morse can be sent because of intersymbol interference. For instance, the first transatlantic telegraph cable of 1858 could only sustain a transmission rate of less than 1 words per minute. This interference is worse with American Morse because it has a greater proportion of closely spaced dots than the Gerke code.

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