Cingular Wireless LLC was the largest United States mobile phone company, with headquarters in Atlanta, Georgia. Cingular, formed in 2001, was a joint venture of the American landline telephone companies AT&T and BellSouth (formerly known as SBC Communications). The two companies held 60% and 40% stakes in Cingular, respectively, based on the value of the assets each company contributed to the venture. Cingular was the second largest mobile phone carrier in the United States. When both companies were acquired by SBC in 2005, the company became a wholly owned subsidiary.