Montgomery County's Agricultural Reserve — Four Decades of Transferable Development Rights to Save Maryland Farmland

In 1980, Montgomery County, Maryland downzoned roughly 93,000 acres in its north into an Agricultural Reserve, cutting allowed density from one housing unit per five acres to one per twenty-five.

The county's Transferable Development Rights (TDR) system was designed to compensate landowners for that lost property value while steering growth into designated Receiving Zones elsewhere, and to protect farmland and stream valleys feeding reservoirs that supply the Washington, D.C. area.

A landowner may build one unit on the sending property but sell the remaining development rights to developers building at higher density in the Receiving Zones, a market mechanism the Lincoln Institute of Land Policy calls the most successful TDR programme in the country by acreage preserved.

The county has preserved 71,594 acres for agricultural use overall, the highest share of county farmland under preservation easement in the United States, with 47,903–48,516 acres protected specifically through TDR easements.

A Resources for the Future evaluation cautions that even in this well-regarded scheme, landowners exercising their one retained right on a sending-area parcel can still produce scattered, low-density residential patterns, so acreage totals alone do not guarantee compact farmland conservation.