Arizona's Metric Interstate: I-19's Unique Highway
Did you know that there is a US Interstate that is only measured using the metric system? Yep! You read that correctly! Interstate 19 in Arizona, which travels from Tucson to Nogales has metric signage and is fully measured using the metric system.
It was first open to traffic in 1962 but not fully completed until 1975, and was chosen by the Metric Board to be the first highway with only metric signage as a pilot project for converting all of the U.S. interstate system to the metric system in the 1970’s. There have been recent attempts to change the measurements to the imperial system (miles); however, the locals have pushed back on these efforts so the change has never been made.
