=Causes of City Growth.=--The causes that have led to the extraordinary growth of cities are partly economic and partly social. With the more general use of labor-saving machinery in agriculture the number of men necessary to cultivate the farms and supply the world with food has decreased relatively, leaving a larger number to engage in the manufacturing and other industries which are generally centered in the cities. One man with a machine can now do the work on the farm which formerly required several, so that fewer farmers in proportion to the total population are needed. On the other hand, the development of trade and commerce and the rise of the manufacturing industries have created an increasing demand for city workers. Many persons are also drawn away from the country by the social attractions and intellectual advantages which the cities offer. In the cities, good schools are abundant and convenient. There also are colleges, libraries, picture galleries, museums, theaters, and other institutions for amusement and education. There the daily newspaper may be left at one's door often for a cent a copy; there are to be found fine churches with pulpits occupied by able preachers; there one finds all the conveniences of life which modern science and skill can provide--everything to gratify the social instinct, and little or none of the dullness of country life. These are some of the attractions that lure the young and the old as well from the rural communities to swell the population of the cities. These are the forces that are converting us from a nation of country dwellers to a nation of city dwellers. =Consequences of City Growth.=--The congestion of the population in the towns and cities has had far-reaching economic, social, and political effects. _Economic Results._--As the city population becomes more dense the number of those who are able to own their own homes becomes less, and thus the city tends more and more to become a community of tenants. According to the census of 1900, while more than 64 per cent of the families of the United States living on farms owned their own homes, less than 35 per cent of those living in cities were owners of the houses they occupied. In New York city the proportion was only about 12 per cent, and in the boroughs of Manhattan and the Bronx it was less than 6 per cent. Of these hardly more than 2 per cent owned homes that were clear of mortgages.