The circa 1760 Gass House and the attached, much larger 1811 almshouse were added to the National Register of Historic Places on April 11, 1977 because the Gass House is a fine example of the Scotch Irish limestone random course method built during the French and Indian War and because it is linked to Patrick Gass, who was born here in 1771 and is remembered as third in command of the Lewis and Clark Expedition and for service in the Indian Wars and the War of 1812. Patrick Gass's father Benjamin and uncle William immigrated from Ireland, built the farmhouse on their plantation called Union, and, as fullers of cloth, built a fulling mill nearby on Falling Spring Creek. Franklin County, chartered in 1784, bought the Gass House and 165 acres in 1808 for $8,203.75 to provide an almshouse, which was built in 1811. Together, the circa 1760 farmhouse and the 1811 almshouse preserve contrasting examples of early American architecture in local limestone, with the more primitive Gass House showing expedient frontier construction and the almshouse showing more advanced methods half a century later. The almshouse was built to higher standards for public use, with shaped limestone blocks, uniform courses, greater stability, a 30 by 54½ foot footprint, larger height and roof, flat arches with center keystones above windows and doors, larger interior bays and rooms, and evidence in the stonework and center of the east wall that it was built in two phases. The 2½ story Gass House, built of nearby field limestone on the frontier between the French and British empires during the French and Indian War, used many unreworked stones of irregular size and shape laid in random layers, with simple flat-stone lintels, unstable walls, a smaller 19-foot-square footprint, smaller window openings, limited height and roof support, and small rooms with an interior footprint of only 290 square feet. The Gass farmhouse stands as a landmark from the early years of European settlement in the Cumberland Valley, where the Conococheague settlement was established in 1734 and Fort Benjamin Chambers was built in 1756 after General Edward Braddock's defeat at Fort Duquesne, all before the establishment of the United States.