{"nrhp_refnum":"86000103","name":"Hale Solar Laboratory","other_names":["Hale Laboratory"],"category":"building","location":{"address":"740 Holladay Rd.","address_restricted":false,"city":"Pasadena","county":"Los Angeles County","state":"CA","lat":34.13326172650005,"lon":-118.1212538766228,"geom_source":"nps_gis"},"listed_date":"1986-01-23","is_nhl":true,"nhl_designated_date":"1989-12-20","areas_of_significance":["Science","Architecture","Invention"],"significance_levels":["national"],"summary":{"what_it_is":"A T-shaped reinforced concrete laboratory and library building at 740 Holladay Road in Pasadena, California, designed in 1924 by Johnson, Kaufman, and Coate in Spanish Colonial Revival style and completed in 1925 for astronomer George Ellery Hale.","why_significant":"The nomination argues the building is significant for its association with its owner-builder George Ellery Hale, an internationally famous astronomer who founded major observatories and helped organize Caltech and the Huntington Library. It was also the site of important solar research, including Hale's refinement of the spectrohelioscope and the first solar magnetograph built in 1952.","narrative":"Built in 1924-25 on a 95 by 300 foot lot in Pasadena, the Hale Solar Laboratory is a T-shaped reinforced concrete building in Spanish Colonial Revival style, with mission tile roofing, roughly plastered walls and deep-set windows. Johnson, Kaufman, and Coate designed it for astronomer George Ellery Hale, who had retired from directing Mount Wilson Observatory. A domed telescope tower rises 30 feet and sits above a 78-foot well leading to a basement spectrograph room. Sculptor Lee Lawrie created two bas-reliefs, and Beatrix Farrand designed the landscaping. Hale used the laboratory in his later years to study the sun, redesigning the spectroheliograph into the spectrohelioscope to observe solar prominences in hydrogen light. After his death in 1938 it continued as a solar observatory, and in 1952 the Babcocks built the first solar magnetograph there. The building remains unaltered, with much of Hale's equipment and library still inside.","period_of_significance":"1924-1952","architect_builder":"Johnson, Kaufman, Coate","architectural_style":"Spanish Colonial Revival","criteria":["A","B"],"status_note":"Described as unaltered since 1924 and in excellent condition, retaining much of the original equipment and Hale's books and journals. It currently houses offices of the Mount Wilson Institute, and a private residence was built on the grounds.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:55:31.239528-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_CA/86000103_NHL.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/86000103/4fd1d7e97b-800.webp","url_1600":"https://nationalhistoricalregister.com/media/86000103/4fd1d7e97b-1600.webp","licence":"CC BY 3.0","author":"Shinku Hisaki (talk)","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Hale_Solar_Laboratory_2008.jpg\" rel=\"noopener\">Shinku Hisaki (talk)</a>, <a href=\"https://creativecommons.org/licenses/by/3.0\" rel=\"license noopener\">CC BY 3.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Hale_Solar_Laboratory_2008.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/123857926","wikipedia":"https://en.wikipedia.org/wiki/Hale_Solar_Laboratory","wikidata":"https://www.wikidata.org/wiki/Q5641417"},"indexable":true,"url":"https://nationalhistoricalregister.com/california/los-angeles-county/hale-solar-laboratory-86000103/"}