ABSTRACT
The subway is a 19th-century idea realized largely in the 20th century. The industrial revolution was the primary catalyst for the advent of underground transportation; without it the iron horse that pulled the trains, the tunneling technology that bored through the earth, and the iron walls that held those tunnels up would have been impossible. The problem of the subway also had its political and social implications. Mass transit meant reform, for increased mobility freed the working classes from the urban center and gave them greater share of the public realm.
