Hoisting banners, beating drums and waving American flags, demonstrators filled Market Street, the main thoroughfare of the city's Financial District, in what was billed as a "Day without Immigrants."
"Todos son inmigrantes," read one sign, expressing in Spanish the notion that nearly all Americans are either immigrants or descendents of people who migrated to this country.
Nestor Puente, a plumber, said he is now a legal resident of the United States, but wanted to march in support of all immigrants--legal and illegal--who he said are working to make this country better.
"I've got to support my people," he said, as musical instruments and chants echoed in the background.
Across the country, hundreds of thousands of people skipped work and school to demonstrate the depth of contributions immigrants make to American society.
Puente said he felt great about the turnout and hopes the efforts get the same attention as the rallies Sunday, in San Francisco, D.C. and elsewhere that protested the situation in Darfur, Sudan.
"They made the front page," Puente said. "What about us?"
As is often the case in San Francisco, the rally spilled over into support for other left-leaning causes as well. Sign-carriers, for example, could be spotted stumping for progressive politicians and protesting the war in Iraq.