formerly American Telephone and Telegraph Co.
U.S. telecommunications corporation.
It was established as a subsidiary of Bell Telephone Co. (founded by Alexander Graham Bell in 1877) to build long-distance telephone lines and later became the parent company of the Bell system. In the early 20th century it gained a virtual monopoly over the U.S. telecommunications industry, and by 1970 it was the world's largest corporation. It developed transoceanic radiotelephone links and telephone cable systems and created the Telstar satellite communications system. Years of federal antitrust litigation resulted in AT&T's 1984 divestment of its 22 regional telephone companies, which were combined to form seven "Baby Bells": Nynex, Bell Atlantic, Ameritech, BellSouth, Southwestern Bell Corp., US West, and Pacific Telesis Group. Many have since merged. In 1996 AT&T divided its operations into three separate companies: AT&T Corp., Lucent Technologies Inc. (composed of the former operations of Western Electric and Bell Laboratories ), and the NCR Corp. AT&T was divided into four units in 2000.