#278- Calvert & Porter Woods Nature Preserve-Montgomery Co., 75.2 acres. Calvert & Porter Woods Nat. Pres. is a 40-AC old-growth wood. It is a National Landmark & contains a heron rookery. This subject parcel (75.7AC) contains high quality forest of similar diversity. The addition will nearly triple the size of this existing property, enhancing its viability on into the future.