Even though sweeping immigration reform legislation has stalled on Capitol Hill and lawmakers have gone home for two weeks of holidays, Monday is expected to be a National Day of Action to draw attention to the future of an estimated 11 million illegal immigrants.

Many demonstrators got an early start on Sunday, signaling that what began as a string of disparate events in select cities has turned into a national outcry.

"We don't have a leader like Martin Luther King or Cesar Chavez, but this is now a national immigrant rights movement," said Joshua Hoyt, director of the Illinois Coalition for Immigrant and Refugee Rights, which has helped organize Chicago-area rallies.

In Dallas, police estimated the crowd at 350,000 to 500,000. There were no reports of violence. The march, organized by LULAC, or the League of United Latino American Citizens, was to wend its way from the Cathedral Shrine of the Virgin of Guadalupe — a symbol of liberation and independence — to Dallas City Hall, according to FOX News affiliate KDFW.

A smaller, similar protest is planned to occur simultaneously in the nearby city of Fort Worth, with some countermarches planned in northern Texas.

KDFW also reports organizers have asked participants to wear white shirts symbolizing peace, and to carry American flags as opposed to Mexican flags because immigration is "an American issue."

Several downtown retailers and sites, including the public library, have closed or were closing early in anticipation of the large crowds.

Activists say the Senate's decision last week not to push a bill that would have given many illegal immigrants a chance at citizenship is neither a cause for celebration nor a lost opportunity — it's a chance to regroup. And that's what they plan to do at demonstrations from Florida to Oregon that include school walkouts and marches.

As many as 65 cities were targeted for rallies, with more than 20 events scheduled on Monday from California alone. Among the day's activities are a rally scheduled in Bakersfield, a candlelight vigil in Los Angeles and a ceremony in San Diego dedicated to immigrants who have died while trying to cross the border illegally.

Cardinal Roger Mahony, who has been at the forefront of the Catholic Church's calls for activism in support of illegal immigrants, planned to lead the Los Angeles vigil.

In Georgia, where the governor is expected to sign a bill that would require verification of legal status before adults could reap many state-administered benefits, as many as 30,000 people were expected to march in an Atlanta protest, said organizer Adelina Nicholls. Her group, Alianza 17 de Marzo, staged a work stoppage last month.

Marchers there have been asked to carry only U.S. flags because organizers fear waving Mexican or other national symbols would inflame what they perceive as an already anti-immigrant public sentiment, Nicholls said.

Religious groups nationwide have been coordinating the protests in recent weeks, along with dozens of unions, schools and civil rights organizations.

Part of their goal has been to recruit more Asian and Middle Eastern immigrants. Most protesters have been Hispanics and high school or university students. In Montgomery County, Md., school officials have told the high school students on spring break that they will earn community service hours toward their graduation requirements if they attend the rallies around Washington, D.C.

Many groups had been preparing to rally since December, when the House passed a bill to build more walls along the U.S.-Mexico border; make it a felony to "aid, abet or encourage" illegal aliens through human smuggling and other actions; and make it a felony, rather than a misdemeanor, to be in the country illegally.

Those mostly local and regional efforts, supported by popular Spanish-language disc jockeys, quickly converted into national plans after hundreds of thousands of people demonstrated in dozens of cities last month, culminating March 25 with a 500,000-person rally in Los Angeles.

Different organizers have different agendas, but they do agree on the need to convert energy from protests into massive voter registration drives.

Voter registration and citizenship education initiatives are set to begin in several states after a "Day Without An Immigrant" campaign planned for May 1, an event that asks immigrants nationwide to stay home from work and school, and refrain from buying U.S. products.

"Marches will only get you so far," said Armando Navarro, coordinator of the National Alliance for Human Rights, a network of Hispanic activist groups in Southern California. "There has to be an electoral component to get the Republicans out of the majority."

Still, opponents of a guest worker program who say the blocked Senate compromise amounts to amnesty are not ready to back down.

"I understand, you know — the Senate, I think, was, quite frankly, intimidated by having hundreds of thousands of people in the streets waving flags, but I don't think we should pass legislation or devise legislation based on how many people you can get out into the street," said Rep. Peter King, R-N.Y., chairman of the House Homeland Security Committee.

"I'm going to have probably several thousand people outside my office today in New York. I mean, you can't allow that to intimidate you," he told "FOX News Sunday."

The Associated Press contributed to this report.