=Explanatory.=--The horizontal black lines below interpret the right-hand column of figures, and therefore picture the annual total mileage of railways operated.--The color below interprets the left-hand column, and therefore pictures the fluctuations in the number of miles built annually. The =Key= explains the shades on the map. The lightest shade indicates an average of less than one-fiftieth of a mile of railway for each square mile of land. The second shade, from one-fiftieth to one-twentieth of a mile of railway, for each square mile of land, etc. KEY TO SHADES ON THE MAP. Less than 1/50 m. to 1 sq. m. =1= 1/50 m. - 1/20 m. " " " " =2= 1/20 m. - 1/15 m. " " " " =3= 1/15 m. - 1/8 m. " " " " =4= 1/8 m. and over, per " " =5= ] Total and Increase. +------+------------------+ | | Miles. | | Years+--------+---------+ | | Built | Operated| +------+--------+---------+ | 1830 | -- | 23 | | 1831 | 72 | 95 | | 1832 | 134 | 229 | | 1833 | 151 | 380 | | 1834 | 253 | 633 | | 1835 | 465 | 1,098 | | 1836 | 175 | 1,273 | | 1837 | 224 | 1,497 | | 1838 | 416 | 1,913 | | 1839 | 389 | 2,302 | | 1840 | 516 | 2,818 | | 1841 | 717 | 3,535 | | 1842 | 491 | 4,026 | | 1843 | 159 | 4,185 | | 1844 | 192 | 4,377 | | 1845 | 256 | 4,633 | | 1846 | 297 | 4,930 | | 1847 | 668 | 5,598 | | 1848 | 398 | 5,996 | | 1849 | 1,369 | 7,365 | | 1850 | 1,656 | 9,021 | | 1851 | 1,961 | 10,982 | | 1852 | 1,926 | 12,908 | | 1853 | 2,452 | 15,360 | | 1854 | 1,360 | 16,720 | | 1855 | 1,654 | 18,374 | | 1856 | 3,642 | 22,016 | | 1857 | 2,487 | 24,503 | | 1858 | 2,465 | 26,963 | | 1859 | 1,821 | 28,789 | | 1860 | 1,846 | 30,635 | | 1861 | 651 | 31,286 | | 1862 | 834 | 32,120 | | 1863 | 1,050 | 33,170 | | 1864 | 738 | 33,908 | | 1865 | 1,177 | 35,085 | | 1866 | 1,716 | 36,801 | | 1867 | 2,249 | 39,250 | | 1868 | 2,979 | 42,229 | | 1869 | 4,615 | 46,844 | | 1870 | 6,070 | 52,914 | | 1871 | 7,379 | 60,293 | | 1872 | 5,878 | 66,171 | | 1873 | 4,097 | 70,268 | | 1874 | 2,117 | 72,385 | | 1875 | 1,711 | 74,096 | | 1876 | 2,712 | 76,808 | | 1877 | 2,280 | 79,088 | | 1878 | 2,679 | 81,767 | | 1879 | 4,817 | 86,584 | | 1880 | 6,712 | 93,296 | | 1881 | 9,847 | 103,143 | | 1882 | 11,569 | 114,712 | | 1883 | 6,743 | 121,455 | | 1884 | 3,924 | 125,379 | | 1885 | 2,930 | 128,309 | | 1886 | 8,100 | 136,409 | | 1887 | 12,872 | 149,281 | | 1888 | 6,801 | 156,082 | +------+--------+---------+ [Illustration: Railways in the United States, 1830-1860. (From Scribner's Statistical Atlas.)