An important function of the Planning Department is participating in the preparation of Master (or Comprehensive) Plans for county facility, park and campus settings. Such plans cover a broad range of facilities including Croton Point ParkPlayland Amusement Park, Westchester Community College, Westchester County Airport and the 500-acre Valhalla Campus which contains the Westchester Medical Center, New York Medical College, the Westchester Correctional Facility and numerous other county offices, laboratories and support facilities. 

Master Plans generally include a set of materials, such as text, graphs, maps, and studies, that define the goals, objectives, principles, guidelines, policies and standards for the immediate and long-range growth, development and preservation of a facility. The plan can, among other things, serve as a basis for infrastructure development, public investment and creation of detailed plans. 

The Planning Department has a long involvement with the formulation of master plans for the Valhalla campus at Grasslands and its subsidiary facilities. The formulation of an overall plan for the campus was initiated in 1971 with the Medical Center Development Study and other plans followed: 1978 Grasslands Development Plan, 1985 Master Plan Update (parking, utilities, housing and design), 1989/90 Development Regulations and the 1991 Grasslands Activity Clusters.