MY WIFE AND SON laughed at me when, for the third time in less than a mile, I stopped our rental car, stepped onto the gravel road and took yet another wholly inadequate cellphone picture of the rolling fields that surrounded us. Soon they clambered out too and fell quiet. We were in the Palouse, a roughly 4,000-square-mile agricultural region that straddles the Idaho-Washington border. Intensely fertile, the region is defined by its dunelike hills, formed eons ago by windblown silt. The hills, gold and green with grains and legumes, undulate without pattern or rhythm; every bend in the road reconfigures the landscape...