PHILADELPHIA - Visits to the Liberty Bell and other historic sites on Independence Mall in Philadelphia are surging dramatically over last summer.

The National Park Service credits the opening of new buildings such as the National Constitution Center, the Independence Visitor Center and the new home built for the Liberty Bell.

In July, Independence National Historical Park reported that 279,041 visitors went to the Liberty Bell, an increase of 106.2 percent over July of last year. Total visitors to all park sites and events were up 30.7 percent over 2003.

Rick Stengel, the head of the Constitution Center, said the spring and summer have seen attendance climbing, which he attributed to "increased cooperation" between the Park Service, the visitor center, and the Constitution Center.

Both Stengel and National Park Service spokesman Phil Sheridan said promotional efforts on the part of city and regional tourism officials contributed to the numbers. Also, they said the terrorist attacks of Sept. 11, 2001, have receded in public memory.

"I think there's a bit of time between 9/11 and now," Sheridan said. "People feel better about traveling."

However, other historic sites still show a fall-off in attendance compared with the period before the terrorist attacks. For instance, Carpenters' Hall, where the First Continental Congress met, had 12,597 visitors in July - up from 11,679 in July of 2003, but well off the July 2001 figure of 20,832.

Similar drop-offs can be seen at the Declaration House, Christ Church, and the home and print shop of Benjamin Franklin, among other places.

William Moore, head of the visitor center, said part of the reason for that lies in the attraction of sites on Independence Mall, which seems to hold visitors to its boundaries.