Answer: Ancient Greece

When you think about an “odometer” today, most likely the very first thing that pops into your head is the odometer on a car—as in, “Better check the odometer to see how many miles are on that old car.” or, at the quick-change oil shop, “Would you mind reading off the miles on your odometer?”

While we think of odometers in this modern context, the history of the odometer reaches back over two millennia. At its heart, an odometer is simply a device attached to a vehicle that measures the distance traveled and any mechanism by which it does so—be it electronic, mechanical, or a combination thereof—qualifies it as an odometer. The earliest evidence we have for the use of an odometer dates back to writings in both Ancient Rome and Ancient Greece (written by Pliny and Strabo, respectively), referencing the measuring feats of two of Alexander the Great’s bematists.

Bematists were specialists in Ancient Greece that served a key role in record keeping and map making by measuring off distances by carefully tracking their steps between places. Alexander’s bematists, Diognetus and Baeton, however, appear to have upgraded their methodology from simple step counting. Although they make no mention of the use of a device in their records, their records themselves stand as testimony to their use of some sort of highly accurate counting device—their measurement of the distance between the ancient cities of Hecatompylos and Alexandria Areion only deviated 0.2 percent from the modern measurement of 531 miles.

We can get an idea of what sort of device they may have used by looking at surviving records from Ancient Rome of simple mechanical devices used by the Romans. The device used by the Romans is believed to be the same kind of device used by Diognetus and Baeton (the first mention of such a device was several centuries earlier in Ancient Greece, and it is likely the use of the device spread throughout the region).

A recreation of the device, seen here, shows the construction of it. The axles engaged with a horizontal wheel on the wagon bed and would turn the horizontal wheel once for every mile traveled. As the horizontal wheel turned, it would drop rounded pebbles from the small holes into a box. By simply ensuring the wheel remained loaded with pebbles and counting the number of pebbles in the box every time they stopped to rest, bematists could easily and accurately keep track of the distance traveled without relying on counting their steps while in transit.