The New York Subway system is the largest mass transit system in the world with 842 miles of track and 468 stations. It is also the fourth busiest public rail system in the world in terms of annual ridership (after Tokyo, Moscow, and Seoul) and the busiest in the Western Hemisphere, running 24 hours a day with over 1.6 billion rides per year. In 1904 the first underground section of the Subway was opened and today about 40% of the New York Subway is above ground.