{"nrhp_refnum":"66000212","name":"Well No. 4, Pico Canyon Oil Field","other_names":["\"Pico\" #4","Pico Canyon,Well No. \"CSO\" 4"],"category":"district","location":{"address":"9.5 mi. N of San Fernando, W of U.S. 99","address_restricted":false,"city":"San Fernando","county":"Los Angeles County","state":"CA","lat":34.36940691950005,"lon":-118.63116056601731,"geom_source":"nps_gis"},"listed_date":"1966-11-13","is_nhl":true,"nhl_designated_date":"1966-11-13","areas_of_significance":["Industry","Commerce"],"significance_levels":["national"],"summary":{"what_it_is":"Well No. 4 (\"Pico\" #4), the 1876 discovery well of the Newhall Field, within an roughly 850-acre historic area in Pico Canyon, Los Angeles County, California, about 9.6 miles north of San Fernando.","why_significant":"The nomination argues that Pico Canyon was the birthplace of California's oil industry and the state's principal oil region in the 1870s and early 1880s. Well No. 4 produced 25 barrels a day in 1876 and about 70 barrels a day after being deepened in 1877, reviving a collapsing industry. Pioneers of the industry trained here, and the Union Oil Company began in the canyon in 1884.","narrative":"Pico Canyon, in the Santa Susana Mountains north of San Fernando, holds the well where California's commercial oil industry took hold. Well No. 4, drilled by C. A. Mentry for the California Star Oil Works Company, began in July 1876 and flowed 25 barrels a day at 370 feet. Deepened to 560 feet in November 1877, it sent oil over the top of its 65-foot derrick and settled at about 70 barrels daily, the most striking production the state had yet seen. A two-inch gravity-fed pipeline linked the field to the Newhall refinery in 1879, the first of its kind in California. Union Oil Company also got its start in the canyon in 1884. The roughly 850-acre area also contains the remains of abandoned derricks, an 1880 two-story hotel for oil workers, now a residence, and an 1880 one-story school. The well still yields about a barrel of oil a day. Because of fire danger, the canyon is closed to the general public.","period_of_significance":null,"architect_builder":"Well drilled by C. A. Mentry for the California Star Oil Works Company","architectural_style":null,"criteria":[],"status_note":"Well No. 4 still produces about one barrel of oil a day and is California Registered State Historical Landmark No. 516. The 1880 hotel is used as a residence, and the features are little altered and well preserved. The area is closed to the public because of fire danger.","vacant_flag":null,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:55:31.770342-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_CA/66000212_NHL.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/66000212/84c291ec49-800.webp","url_1600":"https://nationalhistoricalregister.com/media/66000212/84c291ec49-1600.webp","licence":"Public domain","author":null,"credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Picocanyon.jpg\" rel=\"noopener\">Unknown author</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Picocanyon.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/123857952","wikipedia":"https://en.wikipedia.org/wiki/Pico_Canyon_Oilfield","wikidata":"https://www.wikidata.org/wiki/Q7191006"},"indexable":true,"url":"https://nationalhistoricalregister.com/california/los-angeles-county/well-no-4-pico-canyon-oil-field-66000212/"}