Our core map appeared in the 1878 edition of Rand McNally & Co.'s Business Atlas an annual publication of the now famous firm of Rand McNally. Rand McNally first issued this atlas in 1876 and still publishes it every year as the Commercial Atlas and Marketing Guide. The main intended readers for the atlas were businesses and shipping firms who regularly used to the nation's rail network to ship their goods to customers across the state or across the country. For this reason, these early Rand McNally atlases offer a wealth of information about the early history and geography of the nation's rail system. Rand McNally was well situated to produce this atlas. Founded in Chicago in 1856, the company began life as a job printer that specialized in meeting the printing needs of Chicago-based railroads, including the printing of railroad tickets, timetables, advertisements, and maps. By the mid-1870s, the company had achieved national prominence as a publisher of railroad maps as well, and had begun to specialize in the field just in time for the national rail construction boom.

We have chosen this map of the United States from 1878, because it shows the nation's rail network (in red) at the height of the frenzy for railroad construction that followed the end of the Civil War. There were 36,626 miles of railroad in the country in 1860; by 1890 there were nearly 160,000 miles. The first transcontinental railroad, combining the mainlines of the Union Pacific and Central Pacific railroads was completed from Omaha, Nebraska to Sacramento, California in 1869. The map shows that two further transcontinental lines were nearing completion in 1878. (Completed railroads appear on the map as simple solid red lines. Railroads still under construction were shown as solid red lines marked with small perpendicular hash marks, or hachures. See, for example, the Northern Pacific Railroad as it runs across eastern Washington, Idaho, and western Montana.) The northernmost route, the Northern Pacific Railroad, would stretch from Minnesota to Portland, Oregon by 1883. In the same year, the southernmost route, appropriately named the Southern Pacific Railroad, was completed from Texas to San Francisco, California. Other important transcontinental routes, such as the Atchison, Topeka and Santa Fe, the Great Northern, the Chicago, Milwaukee, St. Paul, and Pacific, and the Western Pacific/Denver and Rio Grande/Missouri Pacific would link the central part of the country with the Pacific coast by 1911, but only portions of these routes were completed or contemplated in 1878.

Though students will recognize the familiar modern outlines of almost every one of the contiguous 48 states, several of these areas were still territories in 1878, including Oklahoma ("Indiana Territory" on the map), North and South Dakota ("Dakota"), Utah, Wyoming, Arizona, New Mexico, Idaho, Montana, and Washington. Note that each of these states had little or no access to railroads in 1878.

The net of railroads is thickest in a broad band stretching from southern New England to Iowa and Missouri, a reflection of the fact that most of the United States' population, industry, and economic power was concentrated in these states. The dense networks of the southern Great Lakes region and the eastern Great Plains also reflect the particularly important role railroads were playing in developing those areas, at once bringing settlers in from the Europe and the Eastern United States, and returning agricultural products to the processing plants of Chicago, St. Louis, and Cincinnati. Note how these cities, as well as Indianapolis and Toledo, Ohio where already major hubs in the national rail network. In contrast, the southeastern states were still suffering from the disastrous economic consequences of the Civil War, and remained poor ground for railroad development. The bald patch in Eastern railroad network stretches from eastern Tennessee to central Pennsylvania, locates the rugged terrain, poverty, and sparse population of the Appalachian Mountains. The natural barrier to railroad construction presented by the Rocky Mountain chain is also already apparent, although the value of the region's mineral resources in states such as Colorado (which became a state in 1836) was encouraging railroad construction in even the most difficult of terrain.

Next to mountains, perhaps the most significant natural barriers to railroad construction were the broad rivers of the central plains. Bridges were expensive to build and the technology and materials required to build spans capable of supporting the weight of a train and stretching hundreds or thousands of feet were new and experimental. The greatest of all these river barriers, of course, was the Mississippi River, which more than a mile wide in many places. One of the reasons why Chicago developed into the most important of all American railroad cities was that directors of its railroads saw early on that Mississippi River bridges would provide their lines with direct access to the great agricultural lands then opening up across the river. The first bridge ever built across the Mississippi was built in 1856 by the Rock Island Railroad Company (eventually, the Chicago, Rock Island, and Pacific Railroad) from Rock Island, Illinois to Davenport, Iowa, effectively linking Chicago to the Great West. By 1878, as the map shows, the river had been bridged in fourteen places between Minneapolis, Minnesota and St. Louis, Missouri. Reading from the northernmost to the southernmost, these bridges were at: St. Paul, Minnesota; Winona, Minnesota; Lacrosse, Wisconsin; Prairie du Chien, Wisconsin; Dubuque, Iowa; Clinton, Iowa; Rock Island/Davenport; Burlington, Iowa; Keokuk, Iowa; Quincy, Illinois; Hannibal, Missouri; Louisiana, Missouri; and St. Louis. The bridge crossings that appear on the map south of St. Louis turn out to be mistakes. Because investment in railroad construction remained small in the South in the decades after the Civil War, no rail crossings of the Mississippi existed in 1878 anywhere between St. Louis and the mouth of the river, not even at the historic crossing points of Memphis and Vicksburg, or at New Orleans. Remarkably, no rail bridge over the Mississippi existed south of Memphis until one was built at Vicksburg in 1930.