AT&T Inc., an abbreviation of its predecessor's former name, the American Telegraph and Telephone Company, is an American multinational telecommunications conglomerate headquartered at the Whitacre Tower in Downtown Dallas, Texas. AT&T is the world's fourth-largest telecommunications company by revenue and the third-largest U.S.-based wireless carrier, behind T-Mobile and Verizon. On the Fortune 500, AT&T ranked 37th among the largest American businesses, with revenues of $122.3 billion. The first company to bear the name "AT&T" was founded in 1885 as a long-distance subsidiary of the Bell Telephone company. By 1899, AT&T assumed management of Bell Telephone's assets and developed a regulated monopoly over the U.S. telephone sector. AT&T's unparalleled dominance throughout telephony often led it to be nicknamed "Ma Bell." On November 20, 1974, the U.S. Justice Department sued AT&T under the Sherman Antitrust Act to break up the Bell System into separate companies. In 1982, AT&T agreed to the divestiture, and the Bell System was reorganized into seven regional telecom companies. AT&T retained its long-lines division, Western Electric, and Bell Laboratories. Wikipedia