AT&T Inc., an abbreviation for its predecessor's former name, the American Telephone and Telegraph Company, is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's third largest telecommunications company by revenue and the third largest wireless carrier in the United States behind T-Mobile and Verizon. As of 2023, AT&T was ranked 32nd on the Fortune 500 rankings of the largest United States corporations, with revenues of $122.4 billion. The modern company claims the history of the original AT&T founded in 1885 and all relevant history is found on the company’s website. The company to bear the AT&T name began as a merger of the SBC Corporation and AT&T Corporation. SBC began its history as the American District Telegraph Company, formed in St. Louis in 1878. After expanding services to Arkansas, Kansas, Oklahoma and Texas through a series of mergers, it became the Southwestern Bell Telephone Company in 1920. Wikipedia