The National Memorial Arch is a monument located in Valley Forge National Historical Park of Upper Merion Township, Pennsylvania. The memorial arch honors the arrival of General George Washington and the Continental Army at Valley Forge, which was the site of their military camp during the winter of 1777–78. Construction on the structure began in …The National Memorial Arch is a monument located in Valley Forge National Historical Park of Upper Merion Township, Pennsylvania. The memorial arch honors the arrival of General George Washington and the Continental Army at Valley Forge, which was the site of their military camp during the winter of 1777–78. Construction on the structure began in 1914 and it was dedicated in 1917.