The Mexico City Metro began operations in 1969 with Line 1, designed to help modernize the city's transportation system. The system has grown extensively since then, now comprising 12 lines covering most of Mexico City. The network was built using a combination of underground tunnels, surface-level tracks, and elevated sections. Notable for its use of icons to identify stations (implemented due to high illiteracy rates when the system opened), the Metro has become an essential part of daily life in Mexico City, carrying over 4.6 million passengers daily.