The Live Map was a glass-enclosed brass dial attached to the outer edge of the driver’s side of the car and linked via a cable to a car’s odometer. Before leaving on your drive, you would purchase one of the company’s 8-inch paper discs with a trip’s directions, put together by The Touring Club of America. Each disc contained a trip’s mileage on the edge of the disc, with each tick mark symbolizing one mile, and supplementary tick marks for every fifth of a mile. Directions were printed alongside key mileage points like spokes on a wheel, describing road surfaces (paved or dirt), intersections, and rail crossings.
From Turn-by-turntables: How drivers got from point A to point B in the early 1900s