Great Meadows National Wildlife Refuge is a twelve-mile river wetlands preserve in Massachusetts along the Concord and Sudbury rivers between Billerica and Wayland. Covering about 3,600 acres, mostly freshwater wetlands, it grew from a 250-acre Concord parcel long known as the Great Meadows. In 1928, Concord resident D. Samuel Hoar bought part of the meadows and built earthen dikes to improve waterfowl habitat, then donated the land to the federal government in 1944, forming the refuge’s core. Expanded in the 1960s, it is known for birdwatching, diverse wetland wildlife, seasonal mudflats that attract migrating shorebirds and waterfowl, and public trails in both its Concord and Sudbury units.