New York City's first subway system officially opened on October 27, 1904, operating along a nine-mile strip from City Hall to 145th Street. Today, in its centennial year, the subway stretches for 685 miles and carries well over four million passengers each day. New Yorkers of every age, nationality, and income level -- -- from commuters and street musicians to evangelists and homeless men and women looking for a warm place to rest -- -- tourists,...