On September 1, 1897, the first underground subway in the United States opened in Boston, MA. Known as the "Tremont Street Line," the half-mile long route initially connected three underground stations to the city's existing above-ground street railway system. On opening day, more than 100,000 people paid 5 cents to take the 3- to 4-minute journey underneath Boston's streets. Today, subways in the United States and Puerto Rico carry an estimated 2.8 million workers aged 16 and over to work every day.

The first subway in China was built in Beijing in 1969 (but it was only handed to civilian control in 1981 and trial operations ended later in the same year; before which credentials were required). The Tianjin Metro followed in 1984