Protesters across America call for immigration reform
But turnout was less impressive this year than in previous years.
In Chicago, Illinois, 3,000 to 4,500 people marched in the city's downtown, police said. Several people carried a large American flag; others held banners or signs.
The early estimate of participants paled greatly in comparison to protests in Chicago in past years: In 2007, numbers reached about 150,000, and the year before, estimates ranged from 400,000 to 700,000.
In New York, hundreds of sign-carrying protesters gathered in Union Square, preparing for a march toward Foley Square in downtown Manhattan.
"We are demanding that the raids and deportations stop," said Teresa Gutierrez, one of the organizers for the New York rallies.
"We are for the rights of all immigrants, whether they're documented or not," she said.
In Milwaukee, Wisconsin, thousands of protesters carrying flags and signs descended on the city for a scheduled march.
The march was scheduled to proceed from the city's southside to a park that overlooks Lake Michigan, said the Web site of Voces de la Frontera, the group organizing that city's march.
Last year, 80,000 to 95,000 people participated, the group said.
Turnout was even less impressive in the nation's capital. About a dozen people began protesting outside of the Republican national headquarters Thursday afternoon and later moved to the Democratic national headquarters.
Another 60 people gathered about noon by the U.S. Capitol's Reflecting Pool where, in the rain, some finished writing protest signs. A group of American Indians joined the demonstration, saying they are often mistaken for illegal immigrants.