SPIRITWOOD, N.D.—A hulking yellow machine inched along Old Highway 10 here recently in a summer scene that seemed as normal as the nearby corn swaying in the breeze. But instead of laying a blanket of steaming blacktop, the machine was grinding the asphalt road into bits.

"When [counties] had lots of money, they paved a lot of the roads and tried to make life easier for the people who lived out here," said Stutsman County Highway Superintendant Mike Zimmerman, sifting the dusty black rubble through his fingers. "Now, it's...