{"nrhp_refnum":"91001145","name":"Etna Furnace (Boundary Increase)","other_names":["Mount Etna Furnace","Aetna Furnace","Aetna Iron Works","See Also:E"],"category":"district","location":{"address":"Roughly, area S and E of Frankstown Br. Juniata R. bend at Mt. Etna, Catherine Township","address_restricted":false,"city":"Mt. Etna","county":"Blair County","state":"PA","lat":40.52077338400005,"lon":-78.17426662196524,"geom_source":"nps_gis"},"listed_date":"1991-09-06","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Industry","Community Planning and Development","Historic - Non-Aboriginal","Architecture"],"significance_levels":["state"],"summary":{"what_it_is":"A boundary increase to the Etna Furnace iron plantation at Mount Etna in Blair County, Pennsylvania, comprising a charcoal iron furnace (built 1808) and the surrounding company, worker, ironmaster and canal-era buildings and archaeological sites. The district is about 12 miles northeast of Altoona along Roaring Run near its confluence with the Frankstown Branch of the Juniata River.","why_significant":"The nomination argues the complex is the most intact iron plantation of the Juniata Valley iron industry and a representative example of the spread of Pennsylvania ironmaking. It is also cited for community planning, with buildings oriented first to the works and later to the canal, and for architecture, including the ironmaster's house and rare log workers' houses. Archaeological potential is noted in the canal remains, furnace area and building sites.","narrative":"Along Roaring Run near the Frankstown Branch of the Juniata River, the Etna Furnace plantation includes a charcoal iron furnace begun in 1808 and a range of stone and log buildings from the 1830s. David Stewart built a gristmill here in 1793, and the cold-blast furnace went into blast in 1808. Henry S. Spang acquired the works in 1823 and expanded production after the Juniata Division of the Pennsylvania Main Line Canal opened in 1832, raising output to 1,200 tons of pig iron a year by 1842. The ironmaster's house, dated 1832, has an ashlar front and coursed fieldstone sides. Surviving workers' houses, a tenant house, a bank barn and canal locks show how the plantation was organized. The nomination regards the group as a rare, well-preserved example of an iron plantation and as a source of information on ironmaking, canal construction and community life.","period_of_significance":"1808-1874","architect_builder":null,"architectural_style":null,"criteria":["A","C","D"],"status_note":"The manager's house is described as vacant and deteriorating; the furnace was stabilized in 1989 with a temporary roof; the tenant house remains in residential use.","vacant_flag":null,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:11:36.248628-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/91001145.pdf"},"photo":null,"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71992424","wikipedia":null,"wikidata":null},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/blair-county/etna-furnace-boundary-increase-91001145/"}