Cesar E. Chavez (1927–1993) is best remembered as the founder of the United Farm Workers of America, AFL-CIO (UFW). A strong believer in the principles of nonviolence, he effectively employed peaceful tactics such as fasts, boycotts, strikes, and pilgrimages. Last Friday, President Obama proclaimed today Cesar Chavez Day:

One of our Nation’s great civil rights leaders, Cesar Estrada Chavez came of age as a migrant farm worker, witnessing the injustice that pervaded fields and vineyards across California. Facing discrimination, poverty, and dangerous working conditions, laborers toiled for little pay and without access to even the most basic necessities. Yet amidst hardship and abuse, Cesar Chavez saw the promise of change—the unlimited potential of a community organized around a common purpose. Today we celebrate his courage, reflect on his lifetime of advocacy, and recognize the power in each of us to lift up lives and pursue social justice.

For more than three decades Chavez led the first successful farm workers union in American history, achieving gains such as fair wages, medical coverage, pension benefits, and human living conditions. However, his work transcended any one movement or cause. Chavez inspired millions of Americans to seek social justice and civil rights for the poor and disenfranchised. He advocated for nonviolent social reform. He was an environmentalist and labor leader. Ultimately, he forged an extraordinary and diverse national coalition of students, middle-class consumers, trade unionists, religious groups, women, and minorities.

Chavez’s motto in life—si se puede (“it can be done”)—embodies the uncommon and invaluable legacy he left behind. The U.S. Postal Service honored Chavez with a stamp in 2003. “He was the champion for hardworking but underpaid workers,” said art director Carl T. Herrman, who designed the stamp. “His life shows that you don’t have to be a wealthy person to make a difference in America.”

To celebrate Cesar Chavez Day, we’ve devised a little contest for you all. Here’s the question: Who famously called Chavez “one of the heroic figures of our time”? Send your answers to uspsstamps [at] gmail [dot] com. Of those who answer correctly, five will be chosen at random to receive an official USPS program from the Cesar E. Chavez First Day of Issue Ceremony held in Los Angeles on April, 23, 2003. You have until midnight tomorrow (Sunday, April 1) to enter. Good luck, and remember, spelling counts!