Bitter Harvest: LIFE With America’s Migrant Workers, 1959

America has transformed its economic landscape (and has seen that landscape transformed by outside forces) so thoroughly in the past half-century that, to a large degree, today’s workplace is a different universe than that of, say, the 1950s. The explosion in service jobs, the collapse of so much of the country’s industrial sector, outsourcing, the digital revolution, “permalancing,” telecommuting—these and countless other developments can make the relative stability of the United States’ post-war economic hegemony seem like something of a Golden Age.

Some sectors of the economy, however, have hardly changed in the past five or six decades—or the past few centuries, for that matter—and perhaps the best example of employment that looks much the same today as it did in the middle part of the last century is the harvesting of crops with migrant labor. The fraught debate about illegal immigration and jobs “stolen” from native-born Americans by undocumented aliens is not going to be settled here. But when we get right down to it, a huge percentage of the fruits and vegetables we eat (and the cotton and other plants harvested in this country) are worked by migrant labor—both “illegal” and native-born.

In 1959, LIFE sent photographer Michael Rougier around the country to document the conditions faced by migrant workers. Rougier traveled from the South Carolina to Upstate New York and west to California’s rich, vast Central Valley. Over the course of several weeks, Rougier took nearly 3,000 pictures, capturing workers and their families struggling though harvest seasons for potatoes, celery, carrots, snap beans, lettuce—workers most of us rarely even think about, but who nonetheless put food on our tables while laboring in conditions that most American workers consider too demeaning, demanding and low-paying to even contemplate.

Incredibly, none of the thousands of pictures Rougier made for the story ever ran in LIFE. A single picture ran in Fortune—but for reasons lost to time, LIFE magazine never published the big migrant-worker story it had obviously planned. After hundreds of rolls of film, thousands of miles of traveling, scores of interviews and a lot of hard research (more than 40 pages of type-written notes accompany Rougier’s pictures in the LIFE archive), the feature was shelved and, by all accounts, forgotten. Until now.

[See more of Rougier’s stellar work in his “Photographer Spotlight”]

Here, LIFE.com offers a relatively small selection of Rougier’s pictures of migrant workers and their families in 1959. As with so much of Rougier’s work, the photographs here are models of a rare kind of empathetic photojournalism, at-once clear-eyed—never flinching from harsh realities unfolding before the lens—and deeply humanistic. Pictures like this don’t simply happen. Instead, Rougier (who died in 2012, at the age of 86) ceaselessly, consciously worked—and worked hard—to portray these laborers’ lives honestly, and with dignity.

After all, they earned it.

Liz Ronk, who edited this gallery, is the Photo Editor for LIFE.com. Follow her on Twitter at @LizabethRonk.