LOS ANGELES -- Thousands of immigration-reform activists took to the streets around the United States Tuesday.

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Demonstrators demanded a path to citizenship for an estimated 12 million immigrants. They also oppose the more than 700 miles of new walls and fences being built along the U.S.-Mexico border. Some also favor a new sanctuary movement that would allow churches to shelter illegal immigrants faced with deportation.

Democratic Party Chairman Howard Dean told a gathering of activists in Miami that an immigration bill currently before Congress is "insane" for requiring many of the nation's 12 million illegal immigrants to return home before applying for citizenship.

More than 15,000 people wearing white and carrying or draped in American flags marched in the streets of downtown Phoenix and downtown Tucson. Phoenix police are estimating between 15,000 and 20,000 people took part in the Phoenix march and rally at the state Capitol as a mariachi band played.

They carried signs saying "Stop the roundups," and, "The sleeping giant woke up forever."

The 2.5 mile march in Phoenix began at the state fairgrounds, with the number of participants swelling along the way.

About 100 counter-demonstrators gathered at the Capitol, and they exchanged shouts with marchers as they arrived. There were no reports of violence.

Roberto Organo, an illegal immigrant who said he crossed the border from Mexico 15 years ago, carried a sign that read, "I have a dream. Peace for all my people."

"We are not criminals," Organo said. "We are looking for work to support our families. It's OK for government to enforce the law but they have to give us a chance."

Tucson police estimate 2,500 people took part in the Tucson march. The marchers covered about 2.5 miles, leaving Southgate Shopping Center and going to the federal building downtown and then to nearby Armory Park for a rally.

"We want just reform," said Mayela Ruiz, another illegal immigrant. "I've been here 15 years. I've worked hard, paid my taxes. I've had no problems with the law and I'm afraid to leave my house. I want a law that would allow me to work and live in freedom but not like a slave."

In Los Angeles, where May 1 protests in 2006 brought out several hundred thousand at various activities, about 25,000 came out for a downtown rally, said police Capt. Andrew Smith, incident commander for the march. Los Angeles Mayor Antonio Villaraigosa and Cardinal Roger Mahony, head of the Roman Catholic Archdiocese of Los Angeles, both strong immigrant supporters, urged students to stay in school.

For the second year, thousands of immigrant rights supporters are expected to take to the streets of Denver. Supporters expect participants from from Fort Collins, Colorado Springs and beyond to converge on Colorado's capital.

Georgia immigrant rights groups seem to be sitting out the nationwide marches and protests. No local group announced any boycott or march Tuesday. And some of the organizers from last year said that's because immigrants in Georgia are afraid of the upcoming implementation of last year's Senate Bill 529. That set of measures, most of which go into effect in July, was considered the country's toughest law targeting illegal immigrants when Georgia lawmakers passed it last spring.

In Chicago, where over 400,000 swarmed the streets a year earlier, police officials put estimates at about 150,000, by far the country's largest turnout.

In Illinois, "Our No. 1 goal is public safety, and we encourage everyone while exercising their First Amendment rights to be respectful of others without interfering with their rights of movement," said Chicago Police Deputy Superintendent Charles Williams. Hundreds of Chicago police, state and county officers and federal agents are lining the march route to Grant Park, TV station WMAQ reported. Protesters chanted slogans in favor of immigration reform, while others beat drums. Signs proclaimed, "Our hard work feeds your families," and, "We are not criminals."

Texas immigration activists are expected to take to the streets of El Paso on Tuesday. Last year's May 1 protest at the Chamizal National Monument caused downtown El Paso to shut down, as many protesters boycotted American goods. This year, protesters will meet near the Santa Fe bridge and cross the Rio Grande at the Juarez monument.

Hispanic rights groups in the Maryland region are organizing a work stoppage to show that they play an important role in the economy. Some leaders in the Hispanic business community aren't supporting the demonstrators. The president and CEO of the Mid-Atlantic Hispanic Chamber of Commerce, Jorge Ribas, said the boycott proves nothing and may have a negative impact on the debate over immigration reform. Ribas also said the immigrant population is so small in Maryland, the boycott might go unnoticed.

Immigrants and their supporters also rallied Tuesday in New York City, calling for immigration policy reform and an end to practices like federal raids and deportations. While hundreds came out, carrying flags and hoisting signs, it was nothing close to the throngs of people who crowded block after city block at the height of last year's protests.