{"nrhp_refnum":"10001198","name":"Arroyo Seco Parkway Historic District","other_names":["Pasadena Freeway","State Route 110"],"category":"district","location":{"address":"CA 110 from 4-Level Interchange in Los Angeles to East Glenarm St in Pasadena","address_restricted":false,"city":"Los Angeles","county":"Los Angeles County","state":"CA","lat":17.925854043500067,"lon":-116.37450433095819,"geom_source":"nps_gis"},"listed_date":"2011-02-04","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Architecture","Engineering","Landscape Architecture"],"significance_levels":["state"],"summary":{"what_it_is":"A historic parkway district: an 8.21-mile, six-lane limited-access roadway (State Route 110, the Pasadena Freeway) running through Los Angeles, South Pasadena and Pasadena, built in three phases between 1938 and 1953.","why_significant":"The nomination presents the parkway as the first grade-separated, limited-access, high-speed divided road in the urban western United States and the first stretch of the Los Angeles freeway system. It also credits City Engineer Lloyd Aldrich's planning and his funding coalition of federal, state and local agencies. The district has 45 contributing resources, including bridges, tunnels, the Four Level Interchange and the roadway itself.","narrative":"This 8.21-mile stretch of State Route 110, known as the Pasadena Freeway, links the Four Level Interchange in Los Angeles with East Glenarm Street in Pasadena. It was built in three phases: the first six miles in 1938-1940, the Southerly Extension in 1940-1943, and the last half-mile of bridges and interchange in 1948-1953. The district has 60 components, 45 of them contributing, including bridges, tunnels, pedestrian crossings, the Arroyo Seco Channel and two maintenance station buildings. Original features include concrete and asphalt paving, rubble retaining walls, native plantings and decorative bridge railings. Its significance rests on being the first grade-separated, limited-access, high-speed divided road in the urban western United States and the starting point of the Los Angeles freeway network. City Engineer Lloyd Aldrich assembled WPA, state gas tax and local support to build it. Apart from a short altered section, the parkway retains substantial integrity.","period_of_significance":null,"architect_builder":"Los Angeles Bureau of Engineering (Merrill Butler); California State Division of Highways; WPA work crews","architectural_style":"Parkways; concrete rigid frame and arch spandrel bridges; Art Deco tunnel; vernacular pedestrian/equestrian tunnel","criteria":[],"status_note":"Still in use as a highway. The only substantial alterations are between the Yale Street Pedestrian Overcrossing and the Stadium Way Overcrossing, which the form says caused about a 30% loss of integrity there.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:54:29.427544-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_CA/10001198.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/10001198/88b0e1c53c-800.webp","url_1600":"https://nationalhistoricalregister.com/media/10001198/88b0e1c53c-1600.webp","licence":"Public domain","author":"Brian Grogan","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Four_Level_Interchange.jpg\" rel=\"noopener\">Brian Grogan</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Four_Level_Interchange.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/123858927","wikipedia":"https://en.wikipedia.org/wiki/Arroyo_Seco_Parkway","wikidata":"https://www.wikidata.org/wiki/Q460788"},"indexable":true,"url":"https://nationalhistoricalregister.com/california/los-angeles-county/arroyo-seco-parkway-historic-district-10001198/"}