Correction: A previous version of this story claimed the metric signage began in the 1980s. The decision was made in 1975.
A unique stretch of highway in southern Arizona could soon lose what many residents say makes it special. The U.S. Department of Transportation (DOT) is proposing to convert the kilometer-based signage along Interstate 19 — the only such highway in the country — to the standard U.S. system of miles, a change that’s drawing concern and criticism from the Green Valley community.
The 63-mile corridor, which runs from Tucson to the U.S.-Mexico border, has long used metric measurements, a decision made in 1975 when Congress passed the Metric Conversion Act as the country considered the system as the standard unit of measurement. The highway was completed in 1978.
In addition to metric units, the highway features mile markers.
But now, DOT spokesperson Nate Sizemore told The Wall Street Journal the agency wants to “restore American standards” by remeasuring the route and replacing the signs.
While no timeline or formal proposal has been released, the local response has been swift. Residents and business leaders say the existing metric signs are not just functional, but a part of Green Valley’s identity.
“What's wrong with being unique?” asked Bill Berkley, a Green Valley resident. “We've got the shortest interstate in the country, and it’s in kilometers, not miles. That’s a winner. There’s not many places in the U.S. where you get a little math problem while you’re driving.”
Randy Graf, President of the Green Valley Chamber of Commerce and Visitors Center, echoed those sentiments, raising concerns about the potential costs to local businesses. “There are a number of businesses that probably have marketing materials listing the exit numbers,” he said. “So changing them would probably come with some expenses.”
Graf also questioned the rationale behind the proposal, noting that of the roughly 4,000 to 5,000 visitors the Chamber sees each year, none have complained about the metric signage. “The thought process in D.C., I guess, was to change I-19 from kilometers to mileage,” he said. “Other than that, I haven’t heard anything.”
Adding to the confusion, Sue Tinnin, communications manager for the Green Valley Council, confirmed the council has not been contacted by federal officials regarding the change.
This isn’t the first time the metric signs have come under scrutiny. In 2009, a similar proposal by the DOT was halted after then-Governor Jan Brewer intervened. Whether this latest push gains traction remains to be seen.
Steve Elliot, Public Information Officer at the Arizona Department of Transportation (ADOT), provided the following statement:
"Kilometer signage on Interstate 19 dates to the time when the federal government planned to convert to the metric system. This coincided with the freeway's completion in the 1970s. I-19 signage remains in kilometers due to strong interest expressed by communities and businesses. ADOT proposed switching to mile markers in 2009 but withdrew the idea based on local feedback wanting to keep kilometers as part of the area's character. Having received no communication from our federal partners on this matter, we have nothing else to offer at this time."
For now, I-19 continues to offer a rare sight for American drivers — signs marked in kilometers — and Green Valley residents seem determined to keep it that way.
KGUN9 has reached out to Department of Transportation but has not yet received a response.
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Joel Foster is a multimedia journalist at KGUN 9 who previously worked as an English teacher in both Boston and the Tucson area. Joel has experience working with web, print and video in the tech, finance, nonprofit and the public sectors. In his off-time, you might catch Joel taking part in Tucson's local comedy scene. Share your story ideas with Joel at joel.foster@kgun9.com, or by connecting on Facebook, Instagram or X.
