Banamex was formed on June 2, 1884 from the merger of two banks, Banco Nacional Mexicano and Banco Mercantil Mexicano, two banks that had operated since the beginning of 1882. Banamex gradually introduced several financial product innovations to the Mexican market including savings accounts (in 1929), personal credit lines (in 1958), credit cards (in 1968), and ATM banking (in 1972). In 1981, the California Commerce Bank was acquired by Banamex. On August 6, 2001, Citigroup Inc. acquired Grupo Financiero Banamex-Accival for US$12.5 billion, which became Grupo Financiero Banamex. This was the largest-ever U.S.-Mexico corporate merger. Grupo Financiero Banamex's operations were integrated with Citibank's relatively small existing Mexico business under the Banamex brand name. Starting October 4th 2016, as part of the investment program to offer best client experience -and as a further sign of Citi’s commitment to Mexico-, Banamex will be known as Citibanamex.