In 1984, the MCADB took initial steps toward developing a county Farmland Preservation Program by adopting the Mercer County Agricultural Development Area (ADA) map. This map indicates areas that have the potential for continued agricultural use, but not necessarily for this exclusive use. The completed map was approved in April of 1985 and amended in 1990, 2006, and most recently in October 2007 as part of the County's Comprehensive Farmland Preservation Plan. Many criteria were used to determine inclusion of land areas within the current ADA including existing farmland, proximity to farmland, existing zoning, soil type, and tillable acreage. The amount of land that can be included is also restricted by law to be no more than 90% of the County's total agricultural land base.

The map has limited regulatory use. It delineates where farmland preservation can occur, and, delineates where CADB review of non-agricultural development projects may occur.