Only three countries on Earth – Liberia, Myanmar, and the United States – use the customary unit system of measurement. In the 1980s, there was a nationwide push toward the metric system here in America, and Arizona is still feeling its effects. I-19 is a metric highway in Arizona that runs between Nogales and Tucson, and it’s the only one in the country. What a quirky claim to fame!

If you frequently spend time in Tucson, chances are you've driven on Interstate 19 at least a handful of times.
dscz/E+ Collection via Getty Imates
The 63-mile highway is located entirely within Arizona, traveling from Nogales to Tucson. Fun fact: it's one of the shortest highways in the country!
Wikimedia Commons/Nick Nolte
Another fun fact about the highway - and what truly makes it stand out from all others - is that its distance signs are measured in meters rather than miles.
Wikimedia Commons/NicAgent
The speed limit signs, however, are in miles per hour.

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This is a result of the push towards the metric system during the 1980s, when the highway was originally constructed.
Wikimedia Commons/Sign: Arizona Department of Transportation, SVG: The Navigators
Unsurprisingly, the signs caused immense confusion among motorist upon their installation.
Wikimedia Commons/Denver Gingerich
As a remedy, the Tucson district of ADOT decided that all new signs would instead use Customary units, and renovations began in 2002.
So if you've never seen the metric distance signs on I-19, keep an eye out the next time you find yourself on the highway.
Wikimedia Commons/elnogalense
They're one of the quirkiest Arizona claims to fame!

Did you know about the metric highway in Arizona? If so, have you ever driven on it? Tell us your thoughts in the comments! Don’t forget to check out our previous article for another quirky find in Arizona.

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Interstate 19, I-19, Nogales, AZ, USA