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We're defining Siouxland in 150 icons. The daily series began Aug. 17. Follow along at siouxcityjournal.com.

NORTH SIOUX CITY | Well, that's weird. Three roadside signs remain in Union County, S.D., from an aborted nationwide campaign to adopt the metric system.

President George H.W. Bush in the 1990s 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.

The state first began placing signs with both mph and kph after Bush signed Executive Order 12770 in July 1991.

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 two decades.

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.