UPDATED 05/01/12 – 6:00 p.m.

CHICAGO (CBS) — About 75 Occupy Chicago protesters held sit-ins outside at least two Bank of America branches in downtown Chicago on Tuesday, before joining a much larger protest rally and march through the Loop in honor of May Day.

The Occupy Chicago protesters teamed up with about 800 to 1,000 protesters in Union Park, at 1501 W. Randolph St., for a pro-union and immigration rally, before marching to Federal Plaza in the Loop.

At about 10:30 a.m.., a group of about 75 Occupy Chicago protesters blocked the Bank of America at 201 S. State St. – the southeast corner of State and Adams streets. As CBS 2’s Roseanne Tellez reports, they would go on to block the entrance at the Bank of America at the corner of Washington and Dearborn streets, before later joining the larger group of protesters at Union Park.

LISTEN: WBBM Newsradio’s Nancy Harty reports

More than two dozen Chicago Police officers were also at the scene when protesters blocked the two banks, but no arrests were made.

Many wore masks or bandannas over their faces.

The demonstrators also protested at the Bank of America Chicago banking center, 135 S. LaSalle St. where extra security guards were dispatched.

Some demonstrators carried a “Chicago Spring” banner, a reference to the Arab Spring revolutions that forced dictators in Tunisia, Egypt, Libya and Yemen from power.

The protesters took issue with Bank of America for getting a bailout, but not giving a bailout to homeowners in foreclosure.

Occupy Chicago organizers were issuing tweets during the protest. The demonstrators said as of 11 a.m., police were blocking them from going into the bank at State and Adams. A group of 15 protesters tried to go in and open accounts, but they were ejected, the tweet said.

Afterward, the protesters decided, in their words, to “sit down and shut up” in front of the bank. The choice of words is a reference to the name given by critics to the ordinance placing limitations on protesters at the upcoming NATO summit, as proposed by Mayor Rahm Emanuel, and approved by the City Council earlier in the year.

After targeting the banks Tuesday morning, the protesters joined the larger May Day rally at Union Park, at Ashland Avenue and Lake streets.

Chicago police estimated there were 800 to 1,000 people at Union Park at the start of their march toward the Loop. Protesters estimated the crowd was closer to 2,000 people.

At Union Park, the bank protesters joined with groups supporting workers’ rights, immigration reform, and a slew of other causes.

Activist Andy Thayer, an organizer of anti-NATO protests during the upcoming summit, fired up the crowd at Union Park.

“As we march against NATO, we reject your world, President Obama. We reject your world, Republican candidates. We are the people who are going to bring change,” he shouted.

Protesters begin their May Day march at Union Park on Tuesday. (Credit: Steve Miller/WBBM Newsradio)

Their march zig-zaged down city streets and ended at Federal Plaza at Dearborn and Adams streets.

May Day marchers at Washington and Racine. (Credit: Steve Miller/WBBM Newsradio)

Chicago Police Supt. Garry McCarthy said the march went “extremely well.” He said the march was peaceful, and no arrests were made.

LISTEN: WBBM Newsradio’s Steve Miller reports

Both protesters and police saw the march as a kind of practice run for protests planned for the NATO summit next month — although police denied that on the record, even though some top brass were on hand during the march.

McCarthy was asked if police learned anything from Tuesday’s rally that could be used later in the month when NATO protests begin in earnest.

“I can’t say that, but I … I’m impressed by … I saw some cops kind of taking it from people, and you know, they were showing a lot of patience, and I saw the bosses stepping in and rotating the cops,” McCarthy said. “So, you know, those are the tactics that we employed. It’s the way that we trained, and it seems to be taking root. So, I liked what I saw today from the department, and I feel pretty good about it.”

Many of the protesters also saw the march as a practice for their anti-NATO protests in a few weeks. Phillip DeVon of Uptown is among them.

“I’m going to be out here protesting that as well, and I think this is maybe a preview to come, and definitely we’re just getting started, that’s for sure,” he said.

Rachael Perrotta says the Occupy movement shares many beliefs of traditional May Day protesters.

“It’s about putting people first – the rights of immigrants and the rights of laborers are directly tied in to the rights of all other people in this country,” she said.

Six years ago, a huge May Day gathering drew some 400,000 people to downtown Chicago on behalf of immigrant rights.

May Day, as a day to commemorate the labor movement, also has its origins in Chicago. On May 1, 1886, labor activists clashed with police in a rally for an eight-hour workday at Haymarket Square, at Des Plaines and Randolph streets.

Three days later, a similar rally began peacefully on Des Plaines Street, but as a labor activist was finishing his speech to the crowd on the night of May 4, 1886, police arrived en masse and ordered the rally to disperse. Someone tossed a homemade bomb towards the advancing officers and one officer was killed in the explosion.

That was followed by an exchange of gunfire between police and demonstrators, although accounts still vary widely as to who opened fire first. In all, more than a dozen people died in the violence, and at least 100 others were wounded.