The Only Metric Highway in the United States

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The United States has an on and off history of attempting to convert to a nationwide use of weights and measures in the country from the United States customary units (i.e. the use of feet, inches, and pounds) to what is known as the International System of Units which uses units such as centimeters, meters, and kilos.

The last such attempt was initiated by the signing of the Metric Conversion Act in 1975 by President Ford.  The voluntarily nature of the Act contributed to an overall inertia in embracing the metric system and the Metric Board was disbanded in 1982 by President Reagan.

One lone adoption of the metric system in the country’s vast network of highways still exists today.  A 63-mile stretch of highway in from Tucson, Arizona to Nogales near the Mexican border is the only metric highway in the United States.  Sign distances along this section of Interstate 19 are provided in meters and kilometers instead of in miles.

There have been some recent efforts to convert the signage back to US customary units but there has been resistance by local retailers and restaurants that advertise their locations based on the kilometer numbered highway exits.

Currently, only three countries in the world have not adopted the metric system as the standard: The United States, Myanmar, and Liberia.

A road sign on Interstate 19 just south of Tucson taken April 18, 2005. Photo: NicAgent, Wikimedia.
A road sign using the metric system on Interstate 19 just south of Tucson, Arizona taken on April 18, 2005. Photo: NicAgent, Wikimedia, CC BY-SA 3.0



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