The William A. Leet and Frederick Hassler Farmstead District, also known as the Leet/Hassler Farmstead or Glenhaven, is a nationally recognized historic district located in Manning, Iowa, United States. It was listed on the National Register of Historic Places in 1999. At the time of its nomination it contained 12 resources, which included four contributing buildings, three contributing structures, four contributing objects, and one non-contributing building.