The Mid-Atlantic Highlands of Pennsylvania, New Jersey, New York, and Connecticut form a 3.5 million acre forested greenbelt beside one of the nation’s most densely populated regions, including Philadelphia, New York City, and Hartford. Stretching from northwestern Connecticut across New York’s Hudson Valley, through northern New Jersey and southeastern Pennsylvania to near the Maryland border, the region includes forested ridges, fertile farms, pure streams, and reservoirs in the rugged foothills between the Appalachian Mountains and the increasingly urbanized Piedmont and Atlantic Coastal Plains. The U.S. Congress designated this landscape nationally significant in the Highlands Conservation Act of 2004. Within it, the Pennsylvania Highlands comprise roughly 1.9 million acres in parts of 13 counties in eastern and central Pennsylvania and have been designated a Mega-Greenway by the Commonwealth of Pennsylvania. The Appalachian Mountain Club, working with conservation and recreation organizations and with local, state, and county governments, is leading an effort to develop the Pennsylvania Highlands Trail Network from the Delaware River at Riegelsville west to the Maryland border in south-central Pennsylvania, and more than 130 miles of the Highlands Trail have been established from Storm King Mountain, New York, to Riegelsville, Pennsylvania.