Over the last three centuries, our nation has built itself up to become the most productive agricultural society in the history of the world. It has done so largely on the backs of people of color, who have planted, picked, and packed the foods we enjoy every day—often for little pay and deplorable conditions.

Until César Chávez came along, farm workers were, for the most part, voiceless and unable to organize. The son of migrant workers, Chávez returned from serving in the U.S. Navy during World War II to work in the fields himself. He began to see the injustices that were occurring around and to him, and instead of staying quiet, like many of those who went before, he did something about it.

Chavez organized marches and boycotts and fasts to bring attention to the plight and power of American farm workers, and his quiet, inspirational leadership would eventually result in the first labor organization for farm workers: the National Farm Workers Association, which would become the United Farm Workers Union.

Sunday is César Chávez Day, and this year marks the 20th anniversary of his death. His importance in humanizing the food system, experts say, cannot be underestimated. As agriculture became more mechanized and productive in the wake of World War II, many Americans didn’t realize hands were still involved in producing their food.

“Cesar pointed that out, brought the humanity back into the food system. That the food system was not just about industrialization – that people were involved,” says Sanjay Rawal, whose documentary film about farm labor, Food Chains, is in postproduction.

One of the farm labor movement’s earliest and most successful actions was a 1966 march with California grape pickers from Delano to Sacramento to demand higher wages. A subsequent call by Chávez for Americans to boycott grapes until workers were paid a livable wage garnered the support of 17 million consumers nationwide and lasted for five years. During these years, farm workers across the country were inspired to organize, and their plight made its way up to the U.S. Senate.

But while Chávez helped bring farm workers out of the shadows, their struggle remains. For his upcoming film, Rawal immersed himself in the lives of farm workers. In Florida, he found tomato pickers who bring home $40 for 14 hours of back-breaking work. Some of these same Florida tomato farms have, in recent years, been scrutinized for their use of unpaid labor—slaves, essentially—who were held against their will and forced to harvest the produce we see in many of our supermarkets.

Thankfully, in the mid-1990s, the Coalition of Imakolee Workers was formed to advocate for the plight of enslaved workers around Imakolee, Florida. Groups like the International Justice Mission took the issue head-on. And the visibility is working: In just the last 15 years, seven cases of forced labor slavery have been successfully prosecuted, resulting in over 1,000 people freed from slavery in U.S. tomato fields. And since it is likely there are still slaves working in the fields of our country, a campaign is underway that asks consumers to demand their grocery stores refuse to buy tomatoes picked by underpaid or unpaid workers.

“The grape of the 21st century is the Florida tomato,” says Rawal, alluding to César Chávez’s famous grape boycott of 1966. “We need to go into our groceries and demand that they not purchase tomatoes that were picked by slaves. Then we can change it. It’s really Cesar 2.0.”

Rawal adds that while labels indicating organic and fairly traded foods have been helpful, there should also be a label that let’s consumers know the workers who produced the food were treated fairly.

Chávez, who would have been 86 on Sunday, would have supported such efforts on behalf of workers. Events and service projects are scheduled throughout the country this week to honor his legacy—especially in California, where it is a state holiday.