The roadometer was a 19th-century device like an odometer for measuring mileage, towed by a wagon, invented in 1847 by William Clayton and Orson Pratt, Mormon pioneers.
History
The roadometer invented by William Clayton and Orson Pratt had cogs and gears made of wood. It recorded wheel revolutions by the mile and quarter-mile. They used their invention to provide an estimate of the distance their party traveled each day between Omaha, Nebraska, and Salt Lake City, Utah. Subsequently in 1849, it was attached to the wagon of Addison Pratt, to be used to record the daily mileage of the Jefferson Hunt wagon train that pioneered the Mormon Road from Salt Lake City to Los Angeles.
References
Roadometer (odometer) Wikipedia(Text) CC BY-SA