Their presence has put the neighbors who care for Kahn - and city officials - in the difficult position of maintaining the park without closing it to outsiders.
"There's always a couple people here sleeping on the bench, washing in the fountain," said Susan Collins, 60, of Bella Vista. They "have no place to go."
Officials from the nonprofit Friends of Louis I. Kahn Park say the problem has worsened over the last few years.
The situation "upsets us because it drives people away," said Constance Moore, president of the group's board. She attributes the growth of the problem in part to the weak economy. Police were called two weeks ago because "a couple of people were in there with pillows, mattresses, and bags of their stuff."
Though problems with the homeless in Philadelphia parks are not new, members of the Kahn nonprofit say issues with lighting in the park may have contributed to the vagrancy and crime.
Bruce Bonner, chairman of the group's fund-raising committee, said at least three lights have been out in the garden on the fenced-off north end of the park. Bonner, a former president of the board of directors who has been volunteering for 20 years, said vagrants had jumped the fence and slept in the area behind the garden and fountain, leaving mattresses and syringes.
He said that there were few problems during the day, but that at night, homelessness, drinking, and drug use plagued the park.
The nonprofit group, formed in 1983 to spruce up the park, has volunteers who maintain the site and its gardens, operating on an annual budget of about $18,000, with power and water provided by the city. The park was named in memory of the late Kahn, a famed architect who designed buildings all over the world. In Philadelphia, his designs include the Richards Medical Center at the University of Pennsylvania.
A solution to the lighting problem has proved elusive. Bonner said the group had appealed to First District Councilman Mark Squilla, who has been working with the Department of Parks and Recreation.
"Once the lighting is fixed," Squilla said, "I think it'll be a big deterrent to the people sleeping and committing crime in there."
Mark Focht, first deputy commissioner for Parks and Recreation, said workers had been to the park at least 15 times in the last few years to repair the lighting or electrical service.
Some of the lights on the park perimeter are not working, Focht said, and a break in an underground conduit required excavation, removal of heavy vegetation, replacement of the conduit, and repair of the wiring. Focht said staff members had been working on the repairs and should be finished this week.
Moore said the group's only recourse, when it has gotten complaints about homeless people in the park, has been to call the police and Project HOME.
Carol Thomas, director of Project HOME's Outreach Coordination Center, said that the organization had gotten three calls about the park in six months and that outreach coordinators usually visited the park once or twice a month to help link people with services.
"We've kept it on our radar as a hot spot," she said.
Thomas said outreach coordinators would go to the park at least once a week to try to help the homeless. During a stop this month, Thomas said, outreach workers found three homeless people, two of whom were not interested in the group's services. One said he had slept at Kahn because it was safe and he normally wasn't bothered there.
When coordinators begin to frequent parks, Thomas said, the homeless usually leave, at least temporarily.
The problem is not specific to Kahn, Moore said. "It's the city's homeless problem, and we do all we can to mitigate it."
Contact Sean Carlin at firstname.lastname@example.org or follow on Twitter @SeanCarlin84.