Navigating by automobile at the dawn of the twentieth century was difficult because maps appropriate for this new mode of transportation were scarce. An early solution to this problem was the route guide. Listing turn-by-turn directions between various cities, route guides helped early motorists navigate a network of unmarked, local roads. This paper focuses exclusively on the Official Automobile Blue Book, the earliest and most popular of the route guides. It contends that the Blue Book series was a precursor to the American road map because the volumes served two important functions of road maps and did so before road mapping matured into a full-fledged cartographic business. The Blue Book commercialized automobile touring and provided di...