In the 30's of the twentieth century, Western Union has become the world's largest telegraph company. Leaving the idea of expansion into Europe, Western Union took up the expansion of services in the U.S. market. In 1877, starting from September, New York City residents began to have the opportunity to check the time on clock with the "time ball", located on the roof of constructed in the same year a new corporate headquarters - Western Union Building. In the early 60s Western Union has put into operation transcontinental microwave system of data transmission via radio waves, completely replacing the web of telegraph poles and wires. July 3, 1884 the company's shares were included in the calculation base for the newly created stock index Dow Jones Transportation Average. In October 2006 the company made an initial public offering of shares on the New York Stock Exchange, becoming independent from First Data company. Thanks to cooperation with Western Union the Associated Press at the end of the XIX century took almost monopolistic position in the U.S. market news. In 1849, Selden and Sibley, the founders of the future Western Union, created the New York State Printing Telegraph Company.