Before the Civil War, most people lived in rural areas.  After World War I, over half of the entire American population lived in cities.  Remember, the movement of people from rural to urban areas is called urbanization.  As cities grew, many were incapable of keeping up with the building and repair necessary to hold everyone.  These areas often lacked fire departments, police stations, schools, and adequate sewers. Low wages kept working families living in tenements, single-room apartment buildings, in areas that were often crime-ridden, dirty, and very overcrowded.