{"nrhp_refnum":"96001128","name":"State Highway 9 Bridge at the Llano River","other_names":["Ms0071-04-018"],"category":"structure","location":{"address":"US 87, 10 mi. S of TX 29","address_restricted":false,"city":"Mason","county":"Mason County","state":"TX","lat":30.661220222000054,"lon":-99.10971960199998,"geom_source":"nps_gis"},"listed_date":"1996-10-10","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering"],"significance_levels":["state"],"summary":{"what_it_is":"A steel Warren polygonal-chord through truss bridge carrying southbound US 87 (former State Highway 9) over the Llano River, about 10 miles southeast of Mason, Mason County, Texas. It was reconstructed in 1935-1936 from an earlier 1930 bridge.","why_significant":"The bridge is significant under Criterion C in the area of Engineering at the state level because of its rarity of type. Texas Highway Department engineers custom-designed its Warren polygonal-chord trusses after a 1935 flood destroyed the original spans. It is described as the only Warren polygonal-chord truss bridge on a state highway in Texas.","narrative":"Carrying southbound US 87 over the Llano River southeast of Mason, this 902-foot bridge combines two 180-foot steel truss spans with concrete girder and steel I-beam approach spans. It was rebuilt in 1935-1936 after a June 1935 flood washed out the two truss spans and center pier of a 1930 bridge. Federal reviewers insisted the structure be raised to clear future high water. Texas Highway Department engineers responded with custom-designed Warren trusses whose floor beams sit flush with the bottom chord, raising the low steel while limiting how far the roadway had to rise. The form identifies it as the only Warren polygonal-chord truss bridge on a state highway in Texas, and its rarity of type underlies its engineering significance. Froemming Bros. of Austin built it, and Pittsburgh-Des Moines Steel fabricated the trusses. A concrete beam bridge added in 1971-1972 now handles northbound traffic, which has allowed the truss bridge to remain in service.","period_of_significance":"1936","architect_builder":"Bridge Designer: Texas Highway Department; Truss Fabricator: Pittsburgh-Des Moines Steel Company of Des Moines, Iowa; Bridge Builder: Froemming Bros., Inc. of Austin, Texas","architectural_style":"Other: Warren polygonal-chord through truss bridge","criteria":["C"],"status_note":"Remains in place serving southbound vehicular traffic on US 87; a companion bridge for northbound lanes was added in 1971-1972.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:54:23.845061-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/54/9698/40969854/content/electronic-records/rg-079/NPS_TX/96001128.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/96001128/31a8836cc3-800.webp","url_1600":"https://nationalhistoricalregister.com/media/96001128/31a8836cc3-1600.webp","licence":"CC BY 4.0","author":"Larry D. Moore","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Texas_hwy9_bridge_llano_river.jpg\" rel=\"noopener\">Larry D. Moore</a>, <a href=\"https://creativecommons.org/licenses/by/4.0\" rel=\"license noopener\">CC BY 4.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Texas_hwy9_bridge_llano_river.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/40969854","wikipedia":"https://en.wikipedia.org/wiki/State_Highway_9_Bridge_at_the_Llano_River","wikidata":"https://www.wikidata.org/wiki/Q110001274"},"indexable":true,"url":"https://nationalhistoricalregister.com/texas/mason-county/state-highway-9-bridge-at-the-llano-river-96001128/"}