NORTH SIOUX CITY | Three roadside signs are all that remain in Union County of an aborted nationwide campaign to adopt the metric system.
The 1990s push by President George H.W. Bush called for interstate highways to display speed limits not only in miles per hour but also in kilometers per hour. The plan died on the vine, yet the signs remain.
On northbound Interstate 29, just north of the mile marker 4 exit for McCook Lake, a sign shows the speed limit at 75 mph as well as 120 kph. A kilometer is six-tenths of a mile.
On the southbound side of the highway near the same exit, two signs inform motorists that the speed limit has dropped to 65 mph and 105 kph.
Signs with speeds in both measurements are relics rarely seen in the United States.
Stacy Schrunk, of North Sioux City, has driven past the Union County signs for years and never noticed them. Not that it would matter.
"The kph on my speedometer is so small that, honestly, I’ve never paid attention to it," Schrunk said.
Along with Liberia and Myanmar, the U.S. is the rare nation that hasn't adopted the metric system. Motorists in most of the rest of the world monitor their speed by kph.
South Dakota Department of Transportation spokeswoman Kristi Sandal said the state first began placing signs with both mph and kph after Bush signed Executive Order 12770 in July 1991. The order mandated a transition to metric measurements for all federal agencies.
As a result, the Federal Highway Administration began working toward the conversion by changing the wording in manuals and converting data collection to metric. Further steps allowed but didn't require states to change signage to dual metric/U.S. customary units.
South Dakota officials decided to get on board with some 1990s metric signage, but the federal push soon languished. The few signs left along South Dakota interstates with dual markings still stand because they haven't needed to be replaced in the intervening nearly 20 years, Sandal said.
"Anything that is dual is left over from the 1990s," she said.
The U.S. Metric Association, headquartered in Northridge, Calif., wants citizens to embrace conversion to the International System of Units, also called the modern metric system. Association president Lorelle Young said having a system based on multiples of 10 is much less confusing than using inch and pound measurements.
Young noted businesses have warmed to the metric system, as evidenced by grocery product labels that list amounts in both metric and nonmetric units. She said average Americans have resisted the switch, in part because they fear it will be hard to learn.
She also pointed to a strong independent streak that says what's worked for a long time is good enough and doesn't need to change.
"They think we are a powerful country and we can use the inch-pound system if we want to -- a false belief. In many professions, for example, science and engineering, American scientists and engineers must use the metric system, as it is the only system used in their disciplines," Young said.