The entire square stands for one square mile of land, and the space at the upper left-hand corner stands for that part of the square mile which the railroad occupies, counting from fence to fence on each side of the road. This comparison is made on the basis of one hundred feet for the "right of way" (the width allowed in government grants), and is useful in connection with the study of the historical maps, especially those of 1880 and 1889, on which the area of some of the States seems to be nearly all taken up with roads, owing to the small scale of the maps. Iowa has the smallest proportion of any in Group 5. The figures show her proportion to be a little over one-seventh of a mile of road to one square mile of area. (Nevada has the smallest proportion of all the States and Territories, viz., a trifle over 1/117 of a mile of line to one square mile.) That part of the map bearing the deepest shade shows at a glance that an unbroken belt, averaging some two hundred miles wide, stretching from Cape Cod to beyond the Mississippi River, is that part of the country best supplied with railways. The lighter shades grouped on either side of this belt show how the mileage grades away north and south. GEOGRAPHICAL LOCATION OF RAILWAYS. On pages 430 to 433 is a series of historical maps showing the location of railway lines at each census-year from 1830 to 1880, and in 1889. Charts comparing and ranking the mileage by States accompany the maps of 1870, 1880, and 1889. These maps and charts give a better idea of the location and extent of progress than could be given by a dozen pages of description and a hundred columns of figures. _Centre of Mileage and of Population._--The space for notes on the maps permits the bare mention of the meaning of the series of stars in the 1889 map (page 433), which mark the centres of mileage and of population. It is well to state the manner of determining the centres of mileage, that it may have its proper bearing in any study of the subject into which the showing may enter. The locations are necessarily approximate. Each centre was determined by selecting, on the proper map, a line running east and west which seemed, to the eye, to nearly divide the mileage into equal parts. The sum of the mileage of the States north, was then compared with that of the States south of the line. By this means the position of the line chosen by the eye was corrected and the right parallel determined. The meridian dividing the total mileage into equal parts was ascertained in like manner. The point of intersection of the parallel and meridian is marked in the map by a star, having the proper date printed to the right of it. The upper series of stars locates the centres of railway mileage, and the lower series the centres of population, as given by the returns of the census of 1880. The following table describes the several locations thus ascertained: _Centres of Railway Mileage._