Assabet River National Wildlife Refuge is a 2,230-acre protected landscape along the Assabet River west of Boston, spanning parts of Hudson, Maynard, Stow, and Sudbury. Its forests, fields, wetlands, and vernal pools support migratory birds, waterfowl, other wildlife, and the rare Blanding's turtle. The land was used by Native Americans, farmed by early colonists, traveled during the Revolutionary War, and walked by Henry David Thoreau. In 1942 it was taken for the Fort Devens-Sudbury Training Annex, later serving military and testing uses that left contamination. After long cleanup, the land passed to the U.S. Fish and Wildlife Service in 2000 and opened in 2005 for conservation and low-impact recreation.