Organizers of Monday's event had hoped that millions of Hispanics and other immigrants employed in the US economy would take the day off from work to demonstrate their central place in their ambivalent host country, which is wrestling with ways to deal with an estimated 12 million undocumented people.
Organizers also aimed for a landmark event that would kickstart a national agitation on the scale of the civil-rights movement, which overcame legal discrimination against the African-American population.
As millions of people dressed largely in white took to the streets across America with almost no arrests, they sent a message that could hardly be ignored.
Again and again, news broadcasts jumped from city to city, but the pictures were always the same: streets filled as far as the eye could see with smiling, chanting immigrants waving American flags in an unprecedented show of unity.
Broadcaster CNN called it a 'pivotal day in the fight for America's future and for who will ultimately be future Americans.'
In California, where a third of all residents were born outside the US, cities and towns large and small were taken over by men, women and families more accustomed to living in the shadows than marching in the streets.
'Look at us,' said Maria Vasquez, who took a day off from working as a domestic help for white families in the affluent Pacific Coast town of Santa Cruz. 'All over the country we are showing our faces, proud of who we are and what we do. America can no longer ignore us.'
Standing next to Vasquez was her employer, Tina Hawthorne.
'I felt it was important to come and support Maria,' she said. 'She's worked for me for eight years. She's a good person with a good family. It's absurd that she's illegal and doesn't have basic human rights.'
Down the road, the owners of the popular Saturn Cafe, like many business owners, were closing for the day.
A huge banner slung across the front of the eatery urged, 'Support the struggle for immigrant's rights.'
'Obviously, we will be losing money, but it will be worth it to make this statement,' said owner Tina Dasch.
Hundreds of thousands of protestors gathered throughout the day in downtown Los Angeles.
According to the Los Angeles Times, the crowds were so large that the city's subway ticketing system was overwhelmed - allowing everyone to ride for free.
'I feel like we're making history,' said Jessica Flores, 21. 'This isn't a small movement. This is huge, huge.'
While the vast majority of participants were of Hispanic descent, sympathizers of all races marched Monday under pro-immigrant banners.
Timmy Srisuphan, a 42-year-old undocumented immigrant from Thailand, has been in Los Angeles for 21 years. Like much of Los Angeles' garment district, her sewing factory was closed Monday, so she decided to participate in the march.
'They are always talking about Mexicans,' she said. 'We are part of this, too.'
In San Jose, the capital of Silicon Valley, tens of thousands of marchers paraded through the downtown district. Juan Martinez of San Francisco said he skipped work as a prep cook at a popular restaurant so he could march with his wife and three children.
'I don't mind losing a day's pay,' said Martinez, who came to the United States in 1997 from Mexico. 'That's better than being a slave for all my life.'
