The United States which fought the Civil War was vastly different from the United States which fronted the world at the close of the Revolution. The scant four million people of 1790 had grown to thirty-one and a half million. This growth had come chiefly by natural increase, but also by immigration, conquest, and annexation. Settlement had reached the Pacific Ocean, though there were great stretches of almost uninhabited territory between the settlements on the Pacific and those just beyond the Mississippi. The cotton gin had turned the whole South toward the cultivation of cotton, though some States were better fitted for mixed farming, and their devotion to cotton meant loss in the end as subsequent events have proved. The South was not manufacturing any considerable proportion of the cotton it grew, but the textile industry was flourishing in New England. A whole series of machines similar to those used in Great Britain, but not identical, had been invented in America. American mills paid higher wages than British and in quantity production were far ahead of the British mills, in proportion to hands employed, which meant being ahead of the rest of the world. Wages in America, measured by the world standard, were high, though as expressed in money, they seem low now. They were conditioned by the supply of free land, or land that was practically free. The wages paid were necessarily high enough to attract laborers from the soil which they might easily own if they chose. There was no fixed laboring class. The boy or girl in a textile mill often worked only a few years to save money, buy a farm, or to enter some business or profession. The steamboat now, wherever there was navigable water, and the railroad, for a large part of the way, offered transportation to the boundless West. Steamboats traversed all the larger rivers and the lakes. The railroad was growing rapidly. Its lines had extended to more than thirty thousand miles. Construction went on during the war, and the transcontinental railway was in sight. The locomotive had approached standardization, and the American railway car was in form similar to that of the present day, though not so large, so comfortable, or so strong. The Pullman car, from which has developed the chair car, the dining car, and the whole list of special cars, was in process of development, and the automatic air brake of George Westinghouse was soon to follow.