This paper describes the in situ treatment of two historic wallpapers in the Longfellow National Historic Site, Cambridge, Massachusetts. The papers, hung in the dining room and parlor, were machine printed. They were installed during the 1880's and between 1844-46, respectively. The defects and deterioration problems are discussed. These include: structural defects involving the plaster and its foundation; support defects; design layer defects: and surface accretions, coating and overpaint. The treatment steps are discussed; they include: structural consolidation; consolidation of the support; cleaning; compensation of support and design; and application of a protective barrier. -- AATA