Driving a long-haul tractor-trailer is as commonplace as the items that drivers carry, from blue jeans to blueberries, from toilet paper for Walmart to farm machinery bound for export. There are 1.7 million men and women working as long-haul drivers in the country. Yet truckers — high up in their cabs — are literally out of view for most Americans.

At a moment when President Trump has ignited a national discussion of blue-collar labor and even climbed into a truck during a White House event, trucking, which was once among the best-paying such jobs, has become low-wage, grinding, unhealthy work. Turnover at large for-hire fleets hauling freight by the truckload — the backbone of the industry — runs an astonishing 80 percent a year, according to a trade group. Looming over the horizon is a future in which self-driving trucks threaten to eliminate many drivers’ livelihoods.

Still, trucking continues to draw plenty of newcomers, reflecting the lack of good alternatives for workers without a higher education (one survey found that 17 percent of truckers had less than a high school diploma). Some have lost better-paying manufacturing jobs in the continuing deindustrialization of America. Others have spent years knocking on the door of the middle class in minimum-wage jobs in fast food or retail. To them, trucking is a step up.

Over two days recently, The New York Times spoke to truckers at the Petro stop, which sits at the intersection of Interstate 57, between Chicago and Memphis, and Interstate 70, between Indianapolis and St. Louis. These interviews were edited and condensed. The maps show drivers’ routes in picking up and delivering their loads.