Valley Forge National Historical Park is the site of a Revolutionary War encampment, northwest of Philadelphia, in Pennsylvania. Washingtonâs Headquarters, a stone house on the Schuylkill River, was occupied by George Washington from 1777 to 1778. Trails connect the key monuments and historic structures, including the early-20th-century National Memorial Arch and the Muhlenberg Brigadeâs recreated log-cabin barracks.