it has been estimated that the modern palmer properly equipped with a labor saving machinery can sew as many acres or harvest as large a crop in a day as fifteen men a century ago thus only a small percentage of the population is needed to to little assuring the country of an adequate food supply perhaps the largest single factor in the growth and development of cities has been the mechanical advances in all forms of manufacturing two hundred years ago the village or small town met all the requirements of the primitive industry of that day there was little demand for power because most goods were made by hand they developed out of steam power and power operated machines made it possible to produce more goods less expensively and more efficiently no longer was the one or two man plants suited to the times factories equipped with complicated machinery replace them and provided employment for large numbers of people this growth led to further growth homes and stores had to be built to supply the workers needs salesmen and office workers were needed to sell the new products banks and other businesses multiplied and gave employment to more people because of the business they could do with industrial farms and their employee this industrial expansion created a need for more adequate transportation to move produce and manufactured goods for domestic in the early days the only means of mass transportation was by water all of the cities of any size were located at harbors or on navigable rivers the mississippi river and its tributaries provided a valuable means of transportation cities were founded and flurries along its course the river boats were used to haul every conceivable article cotton for the mills lumber for building construction farm products and livestock and passengers to settle new territor the great lakes also provided a means of transportation from the eastern seacoast to anyone ports today this area is one of the most heavily populated and industrialized in the united states with the advent of the railroad linking centers of population and providing pastor transportation big cities grew bigger and new cities were created powered to operate trains and factories required coal great centers of population grew near the rich coal deposit as the railroad lines moved westward new city developed where only wilderness had existed before the railroads provided the first overland link between the great harbors and fertile valleys of the west with the huge industrial regions of the with the discovery and development of oil fields a new source of power was procured for our country's ever growing economy the invention of the automobile provided us with another me means of transportation as the automotive industry grew more and better highways were built until today there are hundreds of thousands of miles of paved roads and highways throughout the country connecting every city town and village the development of vast hydroelectric projects especially in the far west brace the last needed source of power to complete our economy a city grows in size its needs become more complex to travel from one part of a city to another presents problems of transportation the early horse drawn street car averaging four miles an hour would be entirely you're not equipped for the large modern city of today electric trolley cars provide a faster and more economical means of transit allowing cities to grow ever larger relieve traffic congestion many cities are built subways under the heavy traffic business areas high speed freeways are designed to permit the rapid movement of motor vehicles to the far reaching sections of the city improvements in transportation within cities that made it possible for people who live in small nearby towns or suburban areas and commute to work in the city with very little loss of time where in a matter of seconds you were whisked to the top floor such a structure could not have been buil development of medical science has an important place among the factors that have made the growth of cities possible during the middle ages cities where time after time devastated by a great plague purification of water supplies disinfection adequate sewerage and inspection of food supplies have removed one of the