Samuel Morse and Alfred Vail were the first to develop a dot-and-dash code for use with an electric telegraph. (Trivia note -- an anagram for "The Morse Code" is "Here Come Dots"). However, the original specification contained a few oddities, such as a long dash for the letter L, plus internal spaces within some of the other letters. So a more regular variation was developed in Europe, which was initially referred to as "Continental Morse", while Morse's original code became known as "American Morse". (A review of these events appears in William G. Pierpont's A Brief History of Morse Telegraphy - Part II).
In addition, the United States Navy briefly used a third variation for radio, called the Navy Code. The Navy's version was based on its existing semaphore "Wigwag Code", where signalling was done by moving a flag to the left or right -- in radiotelegraph usage, the right motions became dots, and left became dashes. However, for radio use the Navy soon dropped its version and switched to Continental Morse, the reason, as stated by Chief of the Bureau of Equipment H. N. Manney in a 1905 report, being that "Experts in two codes are rare; to become expert in three is practically impossible for the great majority of operators."
Eventually, Continental Morse became the world radiotelegraph standard, and was renamed "International Morse", while Morse's original "American" version mostly disappeared from radio use, although it remained the standard for U.S. land telegraphs.
Wireless Course, Electro-Importing Company, 1912, pages 113-114:
Lesson Number Fifteen.
LEARNING TO OPERATE.--THE CODE.--THE WIRELESS LAW.
IN the wireless telegraph, contrary to the wireless telephone which transmits speech wirelessly, it is necessary to learn the code of signals employed in transmitting and receiving messages.
The code is a series of dots and dashes, as they are called, composed of short and long sparks as liberated at the sending station, a certain combination of short and long sparks forming a code letter or figure. As an example, suppose it is desired to transmit the letter A, in the Morse code of signals. This requires that the sending key be closed or depressed for an instant; released, and again depressed for a period slightly longer, the signals sent thus, being known as, Dot-Space-Dash; or a short spark, no spark, long spark. Electro-magnetic waves corresponding to the short and long sparks set up at the sending station, are propagated through the ether, to the receiving station, where they manifest their presence, by short and long buzzes in the receivers, the various combinations being interpreted by the receiving operator.
There are three codes in general use now, for wireless communication, viz.: the Morse, Continental and Navy codes; the equivalent dots and dashes for letters and figures in each code appearing on next page.