The transition from folk to engineered roads in the Mojave Desert

In 1916 the federal government directed the United States Geological Survey (USGS) to begin a program to survey water sources as well as mapping and marking roads in the Mojave Desert, the first federal effort at doing so for automobile routes. Improved highways arrived later but based on an entirely different approach; these were maintained by a highway department which carried out numerous improvements over time based on goals of reducing travel cost. This engineered highway network has little in common with the earlier road network and remains in use today. This research will examine these changing road networks of the Mojave Desert from 1917 to 1940 to identify whether the changing purpose of these routes can explain how one road network so effectively replaced another despite using the same type of vehicles. Maps of the 1917, 1922, and 1940 road networks were digitized and cost distance routes generated in GIS in an attempt to replicate both the 1917 and 1940 networks. The expectation is that the 1940 network was based on optimization while that of 1917 was instead based on creating feasible routes between water sources that avoided physical barriers. The ability of cost distance routes to replicate the 1940 routes but not those of 1917 confirms that these two networks were based on different principles. Despite this transition a few early roads remain in the desert and the mapping work of the USGS remains relevant in the twenty first century.