{"nrhp_refnum":"79002157","name":"Allegheny Observatory","other_names":[],"category":"building","location":{"address":"159 Riverview Ave.","address_restricted":false,"city":"Pittsburgh","county":"Allegheny County","state":"PA","lat":40.48115314650005,"lon":-80.02179455630015,"geom_source":"nps_gis"},"listed_date":"1979-06-22","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Science","Architecture"],"significance_levels":["state"],"summary":{"what_it_is":"The Allegheny Observatory is a classical-style astronomical observatory building on the Northside of Pittsburgh, Allegheny County, Pennsylvania, with three large telescope domes and a rectangular main block. Its new building was begun in 1900 to designs by architect T. E. Billquist.","why_significant":"The nomination argues the observatory is significant for its scientific work, centred on its telescopes and the astronomers who used them. It cites the 30-inch Thaw astrometric refractor as the most successful telescope of its kind, used to measure distances to over 2,500 stars. It also credits the observatory's research on the Sun, Saturn's rings and double and triple stars.","narrative":"Built on the Northside of Pittsburgh, the Allegheny Observatory has a classical layout with a large rectangular block, a pedimented entrance supported by Doric columns, and three large domes that house its telescopes. Architect Thorsten E. Billquist designed the building after an 1896 competition, and the cornerstone was laid on October 20, 1900, on land donated by David E. Parks. The observatory's scientific reputation rests on its instruments. The original 13-inch Fitz-Clark refractor was used by Samuel Pierpont Langley to study solar energy and by James Keeler to show that Saturn's rings are made of particles. The 30-inch Thaw astrometric refractor, completed in 1912-13, has measured the distances to more than 2,500 stars and is one of the few instruments capable of searching for planets around other stars. The observatory also trained generations of student astronomers.","period_of_significance":"1900-1924","architect_builder":"T. E. Billquist (architect)","architectural_style":"Classical","criteria":["A","C"],"status_note":"Continues to serve the University of Pittsburgh and the public, with active research; the Thaw and Keeler telescopes remain in use.","vacant_flag":false,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:11:29.804478-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/79002157.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/79002157/c05716e69d-800.webp","url_1600":"https://nationalhistoricalregister.com/media/79002157/c05716e69d-1600.webp","licence":"Public domain","author":"Tom Murphy VII","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Allegheny_Observatory_2007b.jpg\" rel=\"noopener\">Tom Murphy VII</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Allegheny_Observatory_2007b.jpg"},"district":{"nrhp_refnum":"100006181","name":"Riverview Park","url":"https://nationalhistoricalregister.com/districts/pennsylvania/riverview-park-100006181/"},"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71997772","wikipedia":"https://en.wikipedia.org/wiki/Allegheny_Observatory","wikidata":"https://www.wikidata.org/wiki/Q549937"},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/allegheny-county/allegheny-observatory-79002157/"}