A study of the growth of railroad mileage during a period of years will reveal many instructive features of railroad progress. In the following chapter will be given several tables of statistics showing the growth of the railroad industry, especially during later years. From such tables it is possible to draw conclusions, regarding the present status of railroad business and its probable future growth, which will be of considerable value to the railroad engineer in understanding many of the problems which must be solved. But it should not be forgotten that the proper interpretation of statistics is not easy, and that wrong conclusions may readily be drawn from them. An endeavor will be made to point out some of the legitimate conclusions which these statistics indicate. In Table I is given the mileage in the United States for each year from 1870 to 1910, the increase for each year, the number of miles of line per 100 square miles of territory, the number of miles of line per 10,000 inhabitants, and the total railway capital per mile of line. The figures for the year 1888 and later are taken from the reports of the Interstate Commerce Commission. Those for previous years have been taken from various sources, chiefly the annual issues of Poor's Manual. The figures given in the later issues of Poor's Manual do not agree exactly with those from the Interstate Commerce Commission, although the agreement is sufficiently close for any deductions which we may here wish to draw from the figures. It should be noted that the "number of miles of line" does not consider whether the road has one track, two, three, or four, nor that a mile of line in one place may be worth ten or twenty times a mile of line in some other place. The growth of the mileage may be most readily studied by an inspection of Fig. 1. The steeper the line, the more rapid has been the growth in mileage. The annual increase and its fluctuations are more readily seen in Fig. 2. For several years after the "boom" times of 1870 to 1873 but little was done, until another boom began about 1878-9. This culminated in 1882 and dropped suddenly in 1884-5. After the panic year of 1893 but little was done until 1898-9. Then another boom started which had its culmination in 1906. The panic of 1907 was followed by the usual slump.

The " number of miles of line per 100 square miles of territory" is shown graphically in Fig. 3. Since the area considered is constant, the number constantly increases. The rate of growth is indicated by the steepness of the "mileage curve" and also by the ordinates of the "differential curve." The differences are given in column 4 of Table I.

In column 5 of Table I is shown the "number of miles of line per 10,000 inhabitants." The number reached a maximum in 1893. The check in railroad building caused by the panic of that year caused a gradual reduction in the ratio, which meant that the population was growing faster than the building of railroads. This tendency was not checked until 1899. After that year the prosperity of the country again so increased that it could afford more miles of railroad per 10,000 inhabitants. Apparently following an inevitable law, the next local maximum in this figure was reached in the fateful year 1907, and since then there has been another slump.

Fig. 1. Total railroad mileage in the United States.

The "total railway capital per mile of line" has remained fairly constant. Disregarding the value given for 1870, which is of somewhat doubtful accuracy, the remaining figures are marvelously uniform, until the last few years, when the enormous and revolutionary improvements in road-bed, track, rolling stock and structures have demanded a substantial increase in capitalization. But the great development in the essential value of the roads of the country between 1875 and 1900, with no increase in capitalization per mile, was accomplished chiefly by making improvements out of earnings and perhaps occasionally by requiring fuller payments on stock subscriptions. In general, the capitalization has become a truer measure of money invested than it was,even if the money actually spent came from earnings which were not turned into dividends.

Increase in railroad mileage per year.

Fig. 2. Increase in railroad mileage per year.

Miles of line in the United States per 100 square miles of territory.

Fig. 3. Miles of line in the United States per 100 square miles of territory: also differential curve showing variations in rate of increase.

Table I. Railroad Statistics

1

2

3

4

5

6

Year.

Mileage.

Annual increase.

Number of miles of line per 100 square miles of territory.

Number of miles of line per 10,000 inhabitants.

Total railway capital per mile of line.

Diff.

1870

52,914

6,070

1.78

25

13.72

$44,255

71

60,293

7,379

2.03

20

15.18

59,726

72

66,171

5,878

2.23

14.

16.19

55,116

73

70,268

4,097

2.37

. 14 07

16.71

57,136

74

72,383

2,117

2.44

06

16.76

60,944

1875

74,096

1,711

2.50

.09

16.74

61,534

76

76,808

2,712

2.59

.09

16.87

60,791

77

79,089

2,280

2.66

16.94

60,699

78

81,776

2,629

2.75

.09

16

17.08

58,916

79

86,497

4,746

2.91

.16

17.65

58,070

1880

93,349

6,886

3.14

. .23

18.61

58,624

81

103,145

9,796

3.47

..33

20.06

60,645

82

114,713

11,568

3.86

.39

.23

21.77

60,830

83

121,454

6,741

4.09

.23 13

22.51

61,592

84

125,379

3,825

4.22

12

22.71

60,886

1885

128,967

3,588

4.34

25

22.83

60,897

86

136,338

7,371

4.59

.22

23.61

60,564

87

142,776

6,438

4.81

.22 .15

24.19

58,093

*1888

149,902

7,126

4.96

.26

24.87

59,392

89

157,759

7,857

5.22

29

25.63

58,775

1890

163,597

5,838

5.51

•23

16

26.05

60,340

91

168,403

4,806

5.67

.10 11

26.26

60,942

92

171,564

3,161

5.78

.11 .16

26.22

63,776

93

176,461

4,898

5.94

.16

.08

26.43

63,421

94

178,709

2,247

6.02

.08 06

26.25

62,951

1895

180,657

1,949

6.08

07

26.03

63,206

96

182,777

2,119

6.15

25.84

59,610

97

184,428

1,652

6.21

.06

.07

25.60

59,620

98

186,396

1,968

6.28

.07

Aft

25.41

60,343

99

189,295

2,898

6.37

.09

14

25.35

60,556

1900

193,346

4,051

6.51

a XT

.13

25.44

61,490

01

197,237

3,892

6.64

.18

25.42

61,531

02

202,472

5,234

6.82

.18

25.89

62,301

03

207,977

5,505

7.00

.18 .20

25.74

63,186

04

213,904

5,927

7.20

.20 14

25.96

64,265

1905

218,101

4,197

7.34

.14

21

25.97

65,926

06

224,363

6,262

7.55

.21

26.22

67,936

07

229,951

5,588

7.74

.19 .11

26.38

69,305

08

233,678

3,727

7.85

. 11 .11

26.30

70,872

09

236,869

3,191

7.96

.11

26.20

72,975

1910

240,439

3.605

8.08

.12

26.14

76,444

* For 1888 and later, figures taken from reports of Interstate Commerce Commission. Earlier reports less reliable and accurate.