"During the sixty years between 1910 and 1970, the percentage of Americans living in urban areas of 2,500 or more rose from 45.7 to 73.5, and the number of urbanites more than tripled from 42 to 150 million. Urbanization clearly has brought important benefits to people… But this overwhelming tendency of people to concentrate in cities has worsened the environment through crowding, traffic congestion, delays and loss of time, and the over-loading of transportation, marketing and living facilities."