On the Road, from the Postal Web to Lincoln Highway
By: Paul Kahn
Tags: Postal Service, Roadmaps, Oregon Trail, Data Visualization, Maps

The roads connect 450 post offices concentrated along the coastal plains and river valleys. To indicate distances, numbers appear between towns, a coding system that carried over to later road maps. Three types of roads — Post Roads, Post Roads established by Contract and Post & Stage Roads — are differentiated by shading of the connecting lines. The encoding of road types by different line styles would continue to develop in future maps.

This detail from Bradley’s A map of the United States exhibiting post roads & distances shows a series of hatched Post & Stage Roads connecting in all directions to Philadelphia, with mileage numbers between towns: 20 miles from Philadelphia to Bristol, 12 miles from Trenton to Princeton, etc.

Bradley created the diagram by combining information from commercially available maps, military surveys and distances from reports by local postmasters. The print was distributed to post offices and sold to the general public [3]. The elaborate table that fills the space off the Atlantic coast, “Progress of the Mail on the Main Line,” lists the stages connecting the northernmost town of Brewers, Maine to the southernmost town of St. Mary’s, Georgia. The chart indicates the time of day when the north- and south-bound mail arrives and leaves in each town. This gives the reader a schedule of how long it will take for a letter to travel from town to town. A letter leaving from Portland, Maine at 6 am on Wednesday will take eight days to arrive in Philadelphia the following Wednesday at 7 am.

A detail from the “Progress of the Mail on the Main Line” table in A map of the United States exhibiting post roads & distances. This part is the summer schedule for mail moving southward and northward between Maine and Massachusetts. Arrival and departure times are indicated as forenoon (f) and afternoon (a).

Show Me the Road to Get There

The examples so far have visualized overland travel as potential pathways through a network of a region’s roads. The same problem can be visualized as a single road that leads from our present location and reaches our ultimate destination. A different type of transportation diagram is needed to support a pre-determined journey following a single road.

Sabatele, a man from Tanzania (at the time German East Africa), was hired by the German scientist Karl Weule to support his travels. Sabatele drew a map of the caravan route from the inland start of their journey to the Indian Ocean, which Weule chose to reproduce in his book Native Life in East Africa [4]. In modern European practice, transportation diagrams had become an external rather than an internal representation of spatial understanding. We expect such diagrams to be a record, rather than a performance. Many indigenous peoples who lived by their knowledge of trade networks instead relied on internalized maps and performative means to support overland travel. Weule’s decision to solicit drawings from his African employees with no European education, to see what they could do, is an example of this. European literature is filled with examples of explorers expressing profound surprise when indigenous people, often at the explorer’s request, perform their spatial knowledge by drawing maps on the ground or on supplied materials [5].

“Map of the main caravan road, with its principal branches, drawn by Sabatele, a Mmambew,” from Weule [4]. In his reproduction, Weule rotates the drawing to place north on the top and puts numbers next to 15 identifiable locations.

Weule was able to decode each of the dots, circles and connecting lines in the drawing through discussion with the men he employed. Reading right to left, the visualization represents roads from several possible points of origin on the shores of Lake Tanganyika, Lake Victoria or the area between the lakes crossing rivers, swamps, mountains and deserts, to arrive at the various markets of Dar es Salaam on the Tanzanian coast.

Sabatele’s map of the main caravan routes in East Africa. Paper and pencil. This map with its southerly orientation traces the main caravan routes across Tanzania, with the terminus points placed at Dar es Salaam. Size of the original: unknown. Current location: unknown. Photograph courtesy of the Archiv Museum fur Volkerkunde za Leipzig (Neg. Af 0 1428; from the original glass plate negative). [6]

The map is oriented with south at the top and the coast on the left. In this case, the “legend” of the route map was the context of the request to visualize the caravan roads and share that knowledge through discussion. The lines connecting the circles represent the roads. The lines crossing the road represent natural barriers — rivers and swamps — while the circles inside circles represent places. In this case, the angles of the connecting lines carry useful directional information.

Detail of the cartouche for “The Road from London to Aberistwith” from Brittania. The illustration shows a team of surveyors measuring a road.

John Ogilby’s route maps of Britain are strikingly different from this East African example, yet they share many of the same informational characteristics. Ogilby was neither a caravan driver nor a great traveler. At different periods of his life, he was an English court entertainer in dance and theater, a writer of poetry and classical translation, and a major London book publisher. His fortunes rose and fell and rose again during the turmoil of the English Civil War and Restoration. His calling as an information designer came at late in his life when, at the age of 70, he held the title of Cosmographer to the King in the court of Charles II. In the few years that remained to him, he produced atlases of Africa, America, Japan, China, and Asia, then planned to write and publish Britannia, a multi-volume work that would include a comprehensive history and description of England and Wales.

Britannia, volume the first [7] was the only part of this project that was completed. When the book appeared in 1675, it was the first visualization of an English road network that had previously been described only as lists of place names along selected roads. As part of that project, he participated in a survey of all the roads in the kingdom. Distances were measured by a man pushing a perambulator or measuring wheel beside a mounted surveyor recording the distances. This measuring of the road is illustrated in his book’s frontispiece and the cartouche of several maps [8].