It was indeed conceivable. The enterprise he helped launch that year—the forerunner of the American Telephone and Telegraph Company—would grow into one of the biggest corporations ever seen. At its peak in the early 1980s, just before it was split apart to settle an antitrust suit by the Justice Department, AT&T owned and operated hundreds of billions of dollars worth of equipment, harvested annual revenues amounting to almost 2 percent of the gross domestic product of the United States, and employed about a million people. AT&T's breakup altered the business landscape drastically, but the telephone's primacy in personal communications has only deepened since then, with technology giving Bell's invention a host of new powers.

Linked not just by wires but also by microwaves, communications satellites, optical fibers, networks of cellular towers, and computerized switching systems that can connect any two callers on the planet almost instantaneously, the telephone now mediates billions of distance—dissolving conversations every day-eight per person, on average, in the United States. As Bell foresaw in his prospectus, it is "utilized for nearly every purpose for which speech is employed," from idle chat to emergency calls. In addition, streams of digital data such as text messages and pictures now often travel the same routes as talk. Modern life and the telephone are inextricably intertwined.

At the outset, people weren't quite sure how to use this newfangled device, but they knew they wanted one—or more accurately, two, because telephones were initially sold in pairs. (The first customer, a Boston banker, leased a pair for his office and home, plus a private line to join them.) Telephony quickly found a more flexible form, however. The year 1878 saw the creation of the first commercial exchange, a manual switching device that could form pathways between any of 21 subscribers. Soon that exchange was handling 50 subscribers, and bigger exchanges, with operators handling a maze of plugs and cords to open and close circuits, quickly began popping up in communities all across America. Although the Bell system would stick with operators and plugboards for a while, an automated switchboard became available in the 1890s, invented by an Indiana undertaker named Almon Strowger, who suspected that local telephone operators were favoring his competitors. His apparatus made a connection when a caller pressed two buttons on a telephone a certain number of times to specify the other party. Soon, a 10-digit dialing wheel replaced the buttons, and it would hold sway until Touch-Tone dialing—a faster method that expressed numbers as combinations of two single—frequency tones-arrived on the scene in the 1960s.