marshall trimble ask the marshall true west magazine

How did settlers and cowboys calculate miles?

Jason Bledsoe
Felton, Delaware

Trail riding cowboys had no way to calculate the miles—but the “cookie” driving the chuckwagon could, just like the setters did. They could use an odometer.

roadometer william clayton true west magazine
This diagram illustrates the workings of the “roadometer” invented by William Clayton.

Odometers of some kind have been around at least since Roman times. An early method of measuring miles was to tie a ribbon to a spoke of a wheel, then count the wheel revolutions. This was tedious, and necessity being the mother of invention, the odometer (a.k.a. Roadometer) was invented by Mormon pioneer William Clayton. He used it while crossing the plains in 1847. It used two gears. The rear wheel of a typical covered wagon made 360 revolutions per mile. An odometer was connected to the wheel by a wooden spindle with six small spokes joined to an 18-inch-long wooden “worm gear” of shaft. The large, slower-turning gears of the odometer kept track of up to ten miles at a time. A person was responsible for recording each 10-mile increment counted by the odometer.

william clayton true west magazine
William Clayton.

Marshall Trimble is Arizona’s official historian and vice president of the Wild West History Association. His latest book is Arizona Outlaws and Lawmen; The History Press, 2015. If you have a question, write: Ask the Marshall, P.O. Box 8008, Cave Creek, AZ 85327 or email him at

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