and took on its branding, with the merged entity naming itself AT&T Inc. In 2005, SBC purchased its former parent AT&T Corp. The latter changed its name to SBC Communications Inc. AT&T antitrust lawsuit resulted in the divestiture of AT&T's ('Ma Bell') local operating subsidiaries which were grouped into seven Regional Bell Operating Companies (RBOCs), commonly referred to as 'Baby Bells', resulting in seven independent companies, including Southwestern Bell Corporation (SBC).

In 1899, AT&T became the parent company after the American Bell Telephone Company sold its assets to its subsidiary. The American Bell Telephone Company formed the American Telephone and Telegraph Company (AT&T) subsidiary in 1885.

The latter was a successor of the original Bell Telephone Company founded by Alexander Graham Bell in 1877. After expanding services to Arkansas, Kansas, Oklahoma and Texas, through a series of mergers, it became Southwestern Bell Telephone Company in 1920, which was then a subsidiary of American Telephone and Telegraph Company. The company began its history as the American District Telegraph Company, formed in St. ĭuring most of the 20th century, AT&T had a monopoly on phone service in the United States. As of 2022, AT&T was ranked 13th on the Fortune 500 rankings of the largest United States corporations, with revenues of $168.8 billion. It is the world's largest telecommunications company by revenue and the third largest provider of mobile telephone services in the U.S. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas.

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