By Peter Bowes
BBC News, Los Angeles
The wholesale vegetable markets stood quiet. The perfectly manicured lawns of Los Angeles' rich and famous went untended. Traffic on the freeways was strangely quiet during the rush hour.
May Day is not an official holiday here, but it certainly felt like one. It was not "business as usual" in America's second-largest city.
Los Angles saw two mass rallies
The vast majority of large organisations, Hollywood studios and the court system all remained open. The city did not grind to a standstill, but the "day without immigrants" had a significant impact.
On some streets in LA's downtown, including the garment district, the shutters remained closed on every store.
Many small business owners opted to shut down for the day as gesture of support for their immigrant workforce.
Some posted a notice saying: "United in peace: out of respect for members of our community our stores are closed today, May 1."
"Everybody forgets how much we contribute to the economy," said Vincente Amador, a small business owner who gave his staff of seven workers the day off to join the demonstration.
LA schools were officially open, but some reported truancy rates of up to 30%.
Others, in areas close to the demonstrations, chose to leave their gates chained for the day.
At a march and rally, protestors wearing white waved the American flag and chanted "Si se puede!" - Spanish for "Yes it can be done!"
Others carried banners urging the US Congress to grant citizenship to illegal immigrants.
"We as immigrants should unite and come together because my parents came here illegally," said Sal Diaz, one of the protestors.
"If it wasn't for them, I wouldn't be where I am now, in college, graduated and all."
'Swamped by migrants'
A handful of people took to the streets to object to the assertion, by illegal immigrants, that they should be made citizens of the United States.
More than a million people protested in Los Angeles
"They come here and swamp our social services," said Betty Jo Young. "Our country will be a Third World country if people don't stand up and say 'That's enough'."
Wiley Drake added: "The boycott as I understand it is to make illegal migrant workers legal in America. That's wrong, it's against the law and it's unprincipled."
The day of action did not receive universal support from immigrant workers.
The United Farm Workers' Union urged its members to take part in rallies after work, to avoid being fired.
The union supports a comprehensive immigration reform package and a measure that would legalise 1.5 million farm workers over the next five years.
Giev Kashkooli, an officer with the union, said if the US turned its back on the immigrant workforce, the consequences would be far-reaching:
"Americans would not be eating fresh fruit and produce, it's very, very simple.
"If they really could figure out a way to deport 10-12 million people the agricultural economy as we know it would totally collapse."
A rallying call heard at immigration rallies around the country has been "Today we protest and tomorrow we vote".
Much has been made of the prospect of a rapidly emerging immigrant movement with political teeth. With millions taking to the streets, the rallies are reminiscent of the civil rights protests of the late 1960s.
"There's a whole lot of truth to that," said Abel Valenzuela, an associate professor of urban planning and Chicano studies, at the University of California.
"I think congressmen and women in Washington DC better be paying a whole lot of attention to that."
Much attention is being paid to the attitudes of young Hispanic Americans. They are said to be angry and motivated.
"Of the Latin population below 18, 86% of them are US-born and documented," said Prof Valenzuela.
"That group is becoming exposed to the power of organising, of politics, of marches and protest. And research shows they're more likely to vote.
"So in a few years you're going to see these people actually going out there and voting. I think in many ways what we're seeing on the streets today will, in fact, have an impact in the future."