One short boulevard - 10 tents and a structure of cardboard and tarpaulins - was reserved for families with children, no smoking allowed.
Mayor Nutter walked through the encampment in late afternoon, wearing a yellow shirt and chatting amiably with participants.
"He said that a lot of the things his administration stands for we stand for as well," said Steve Ross, 26, who lived in West Kensington until last week but who now says his home is Dilworth Plaza.
Medical volunteers said they had been able to handle all their problems so far with a couple of adhesive bandages.
But Ross, a member of the protesters' media committee, said organizers were concerned about a forecast of showers or thunderstorms on Wednesday.
They were seeking donations of plastic bins to store medical supplies and wooden pallets to place under tents and other shelters, Ross said.
The duration of the protest remains open-ended. "We'll stay till things change," said Nicole DiPonziano, 23, a graphic designer sporting turquoise-tinted hair.
"There is no end date," Ross said. "We're planning for snow, we're planning for spring rains, we're planning for summer heat. We're staying until our demands are met."
The group's demands have not been fully specified and will be decided at future collective meetings, Ross said.
The protest is being run day-to-day by an assortment of committees dealing with different issues: food (distributing donated food at regular mealtimes, with snacks of apples and peanut-butter-and-jelly sandwiches available in between); medical; safety (with its own volunteer security force, quietly discouraging the use of alcohol and drugs); families; homeless outreach; sanitation; technical support (handling the group's website, www.occupyphilly.org), and comfort (distributing donated clothing and blankets).
Ross said the organizers hoped to arrange for portable toilets to be made available within several days. In the meantime, participants have relied on toilets made available by nearby churches and businesses.
Plainclothes police officers were stationed around Dilworth Plaza and uniformed officers took up spots on the other side of City Hall.
Contact staff writer Bob Warner at 215-854-5885 or email@example.com.