1:20 p.m. ET: The protest today in lower Manhattan is expected to be Occupy Wall Street’s largest demonstration yet. Organizers are planning for at least 2,000 people to participate and the movement is getting a significant boost from at least 15 major labor unions that are joining today’s rally and march.

The AFL-CIO, United Auto Workers, and Transit Workers’ Union are a few of the groups planning to stand in solidarity with the hundreds of primarily young adults who have spent the better part of three weeks organizing from Zuccotti Square.

Today’s action is scheduled to begin at 3 p.m. ET, when the protesters in Zuccotti Square march approximately one mile north to Foley Square, where they will be met by community and labor leaders. Then, at 4:30 p.m., they plan to match together back down toward Wall Street. They do not yet have a city-issued permit for the gathering, but are now pursuing one.

Organizers are also calling on college students around the country to protest by walking out of class at 2 p.m.

ABC News’ Dan Harris toured Occupy Wall Street’s community in Zuccotti Square on Monday.

ABC News’ Gregory J. Krieg contributed to this report.