Such a show of force could help revive a movement that grabbed the public imagination last summer and fall as thousands formed Occupy encampments in cities across the country to protest income inequality and other problems.
The gathering starts Saturday at 9 a.m. at Independence Mall and ends - or begins anew, depending on your interpretation - Thursday at 11 a.m. when they step off on a 99-mile march to Wall Street.
In between, participants will feed the homeless in defiance of Mayor Nutter's ban on doing so in city parks, protest questionable bank deals that cost the city and the school district millions, see a circus, and, well, it's Occupy - almost anything could happen. Bongo drums undoubtedly will be involved.
The whens and wheres of the individual events planned for the National Gathering are not firmed up, but some details are available at occupynationalgathering.com.
At a press conference Thursday, Mayor Nutter and Police Commissioner Charles Ramsey said they would have extra police on the streets through July 4 in connection with multiple events, including the Wawa Welcome America! festival and the gathering. They said they were not especially worried that Occupy participants would cause problems.
Nate Kleinman, who also is handling media calls for the gathering, said people who want to attend should first go to the information table that will be open at 5th and Market Streets during the event.
"Because we don't know what to expect, we are leaving some flexibility," he said.
Speakers include Pulitzer prize-winning journalist Chris Hedges, Rolling Stone reporter Matt Taibbi, Reverend Billy from The Church of Stop Shopping and Wikileaks journaliast Alexa O'Brien.
Philadelphia police evicted Occupy Philly from its very public encampment on Dilworth Plaza in November. That took the spotlight off the group, but Kleinman said members had continued to work for change, including attending protests for school nurses who were laid off and cleaning and greening vacant lots around the city.
Starting July 1, participants in the gathering will meet nightly at 8:30 on Independence Mall to talk about creating what they call a "people's blueprint" for what they want the future will look like.
"It's to say when we say we want a better world, what do we envision," Kleinman said.
And yes, they might camp, but they will not say where. In a release touting the gathering as "five days of Peace, Love, and Democracy," the organizers said:
"Exact location(s) where protesters will be sleeping will not be publicly announced. We may take city sidewalks outside of Too Big to Fail Banks in protest of the unabated crimes these institutions continue to commit, as well as in solidarity with our homeless brothers and sisters."
The other Occupy-related group will not camp. They will stay in hotels and meet at the Convention Center Monday through Wednesday
They also got a permit from the city for a march Wednesday from the Convention Center to Independence Mall, where they will hold a rally.
And while the two groups are not enemies, they are not exactly friends, either.
Steve Cickay, who lives in Newtown, Bucks County, is attending the Convention Center event, which is called Continental Congress 2.0. Organizers hope 700 people will participate.
More information about their goals is here: http://www.the99declaration.org/. It grew out of Occupy Wall Street in New York but quickly broke away from it.
One of the biggest differences between the two groups is that Occupy movements generally work outside the system. Continental Congress 2.0 is trying to attack from the inside.
"We respect the Occupy Movement because they have brilliantly captured the attention of the American public about the gross disparity in wealth in our country and the need to correct the influence of big money. But we believe we need to go further and work within the political process to effect permanent change that is supported by most of the American public," Cickay said in an e-mail.
The group is especially concerned about the influence of money on politics and aims to get some of its members elected to office from a third party.
Contact staff writer Miriam Hill at 215-854-5520, firstname.lastname@example.org or @miriamhill on Twitter.