AT&T

AT&T Inc. is an American multinational conglomerate holding company, Delaware-registered but headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company, and the second largest provider of mobile telephone services. Since June 14, 2018, it is also the parent company of mass media conglomerate WarnerMedia, making it one of the world's largest media and entertainment company in terms of revenue. As of 2020, AT&T was ranked 9th on the Fortune 500 rankings of the largest United States corporations, with revenues of $181 billion. AT&T Inc. began its history as the American District Telegraph Company, formed in St. Louis in 1878. After broadening service 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.