"Box" Telephone, 1876, invented by Alexander Graham Bell
 
While Alexander Graham Bell was experimenting with telegraph instruments in the early 1870s, he realized it might be possible to transmit the human voice over a wire by using electricity.
 
Bell's interest in electricity continued and he attempted to send several telegraph messages over a single wire at one time. Lacking the time and skill to make the equipment for these experiments he enlisted the help of Thomas A. Watson from a nearby electrical shop. The two became fast friends and worked together on the tedious experimentation to produce sounds over the "harmonic telegraph." It was on June 2, 1875, while Bell was at one end of the line and Watson worked on the reeds of the telegraph in another room that he heard the sound of a plucked reed coming to him over the wire.
 
The next day, after much tinkering, the instrument transmitted the sound of Bell's voice to Watson. The instrument transmitted recognizable voice sound, not words. Bell and Watson experimented all summer and in September, 1875, Bell began to write the specifications for his first telephone patent. By March 1876 he managed to make a transmission, but the sound was very faint. The patent was issued on March 7, 1876. The telephone carried its first intelligible sentence three days later in the rented top floor of a Boston boarding house at 109 Court Street, Boston.
 
Bell announced his discovery, first in lectures to Boston scientists and then at the Philadelphia Centennial Exposition to a panel of notables including Brazilian Emperor Dom Pedro II and eminent British physicist William Thomson. The emperor exclaimed, "My God! It talks!" Thomson took news of the discovery across the ocean and proclaimed it "the greatest by far of all the marvels of the electric telegraph."
 
By the summer of 1877, the telephone had become a business. The first private lines, which typically connected a businessman's home and his office, had been placed in service. Bell, Sanders and Hubbard formalized their relationship by creating the Bell Telephone Company, the direct corporate predecessor of today's AT&T. Bell Telephone issued the first telephone stock to seven stockholders. The initial telephone exchange opened the following year in New Haven.
 
From the telephone's earliest days, Bell understood his invention's vast potential. He wrote in 1878: "I believe in the future wires will unite the head offices of telephone companies in different cities, and a man in one part of the country may communicate by word of mouth with another in a distant place."