Ranger Smith walks up to the Dunkin’ Donuts at Seventh and Market and pulls his hat low, down over his eyes, so that the needle heads he’s been following don’t recognize him.

"That's Aaron, on the phone," says Ranger Smith, a U.S. Park Ranger who's asked to remain anonymous. "The girl is Sarah. I see she got her pit bull back. The last time we arrested her, she had six dozen condoms on her. See the other guy? That's Sarah's boyfriend."

What do the three scruffy young white kids have in common and why is Ranger Smith so interested in what they are doing?

They are just three of the dozens of drug addicts -- mostly scruffy young white kids -- who have been infesting Independence National Historical Park in the last month. Perhaps a spillover effect, Ranger Smith surmises, from the successes of Operation Safe Streets many blocks to the north, these three and many others like them have found a new shooting gallery in the place where Ben Franklin and his crew risked life and limb to form a new country.

Ever since 9/11, Independence National Historic Park has been a fairly intense place, the barriers on Chestnut Street just the most visible sign that all is not quiet on the Liberty front.

But as they wait for the moment everyone hopes will not happen, the people whose job it is to guard over Independence Hall and the Liberty Bell are dealing with another problem.

"In the last week, we have had contact with at least nine or 10 junkies and a total of five arrests," says Ranger Smith. "I'm not sure if they are moving down this way. They are buying stuff on Market from Fourth to 13th Street and they are coming here to shoot up and because they feel safe."

And why not? With all the police and park rangers around, the chances of a junkie getting jumped are far less then, say, at Fifth and Lehigh. And that wonderful new visitor's center? Oh, it's a great place for visitors. But also an oasis for addicts.

"We made one drug arrest there last week, a boyfriend and a girlfriend," says Ranger Smith. "But, more and more, we are seeing junkies come in to use the bathroom to clean up and they are going into the movie theater after they shoot up to nod off."

On Sunday, says Ranger Smith, "We had three separate contacts with individuals on Market Street. Two of them had needles, residue and stuff like that. The third one had possession."

On Monday, says Ranger Smith, at about 9 a.m. between Market and Fifth and Sixth, park rangers arrested a 25-year-old woman from Pottstown.

All over the park area, rangers have been finding empty heroin packets bearing brand names like "%" and "Legend" and "Al Pacino" and the aptly named "Fatal Attraction."

"We have very recently, over the last few weeks, seen an increase in the number of drug cases" in and around the park, says INHP spokesman Phil Sheridan. "We have seen increased incidents of use and possession."

Sheridan is quick to point out that while drug use is on the rise around the Liberty Bell and Independence Hall, overall, crime rates haven't changed.

"In terms of the kinds of crimes you would see with the increase in drug use -- robberies and car break-ins -- everything has remained the same over the last few weeks," says Sheridan.

As we walk east again, back toward the bell, Aaron, Sarah and their posse cast nervous glances at Ranger Smith and me.

And while the crimes normally associated with drug addiction haven't spiked here yet, tourists are being confronted with an ugly reality.

"We are seeing increased solicitation for money," says Ranger Smith. "Just yesterday, we stopped Aaron for panhandling in front of the Liberty Bell. We gave him a ticket to appear in court."

Park officials, says Ranger Smith, are also being confronted with a large increase in the number of homeless around here.

Leading me to the corner of Sixth and Ranstead, across from the park, Ranger Smith points to some shrubs where more than a dozen homeless had encamped until recently.

"The dealers have moved and the drug addicts follow the dealers," he says. "Don't get me wrong, I think the Philadelphia Police Department is doing an excellent job. But arrests really don't solve the problem. Treatment and medication is the best way to solve the problem."

"We have increased patrols and we have more people out patrolling," says Sheridan. "These things are crimes. It goes with our mission. We have to protect the buildings against terrorism, but we have a mandate to keep visitors safe and make for a good experience."