The burglary happened sometime after the museum closed at 5:30 p.m. on Tuesday, state police said. The thefts were discovered by a maintenance man about 8 a.m. on Wednesday.
Police said the thieves broke through a main gate and drove down a long driveway to the riverside estate. They then cracked open a door on the ``best kitchen,'' which is next to the main house.
Police said that the museum was equipped with an alarm system but that it did not go off Tuesday night. Rod Snyder, a spokesman with the Pennsylvania Historical and Museum Commission, which owns the museum, said that the alarm system was working but that he did not know why the break-in had not activated it.
The museum, one of Bucks County's main tourist attractions, is a reconstruction of the famous Quaker's country house based on his original design. All that survives of Penn's original house is the foundation.
Museum staff and volunteers, who guide visitors through the main house and elaborate formal gardens, were shaken by the burglary.
``For many of our staff, it's similar to having your home broken into,'' said Mary Ellyn Kunz, the museum's acting director. ``We're very attached to these objects. It's just devastating. When you spend so much of your time here and it's your job to make these things come to life - it's like missing an old friend. There is a real sense of loss.''
In the Great Hall, a long wooden table was covered in cream-colored linen and set with silver spoons, thick jugs and glasses. Absent from the table was the pewter platter, engraved with the initials of Penn and his wife, Guilielma. In its place was a circle of clear plastic, designed to protect the antique.
Similar pieces of plastic were scattered throughout the house, marking the spots where items were stolen.
