Swift River Reservation is a four hundred thirty-nine-acre protected landscape in Petersham, Massachusetts, centered on the East Branch of the Swift River and managed as open space with about seven miles of trails for hiking, horseback riding, mountain biking, and cross-country skiing. Its three contiguous parcels contain ledges, river corridor, woodlands, wetlands, and scenic overlooks, and together preserve a varied rural landscape. Once farmed until the late 1880s and partly cleared by small mills, the land later returned to forest as agriculture moved west and local industry declined. Surviving cellar holes connect the reservation to that earlier working countryside, now part of a broader regional network of protected land.