On Saturday, August 20, historian Bonnie Halda will deliver an illustrated lecture about the centennial of The National Park Service and the 50th anniversary of the Historic Preservation. The location couldn’t be more appropriate: The historic Trent House, a landmark on the Delaware River in Trenton, built in 1719. Ms. Halda is program manager for Preservation Assistance in the Northeast Regional Office of the National Park Service. Her talk will be followed by light refreshments and tours of the house and gardens. Admission is $10 ($8 for members). The event begins at 1 p.m. The Trent House is at 15 Market Street. Call (609) 989-3027 for information.