{"nrhp_refnum":"94000239","name":"Ohio State Route 51 Bridge Over the Portage River","other_names":["Structure No. 6201202"],"category":"structure","location":{"address":"OH 51 over the Portage R.","address_restricted":false,"city":"Elmore","county":"Ottawa County","state":"OH","lat":41.477032198000074,"lon":-83.29556619099998,"geom_source":"nps_gis"},"listed_date":"1994-03-17","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering"],"significance_levels":["state"],"summary":{"what_it_is":"A three-span, closed spandrel reinforced concrete arch highway bridge carrying Ohio State Route 51 over the Portage River at Elmore, Ottawa County, Ohio. Construction ran from 1926 to 1927 at a cost of $50,000.","why_significant":"The nomination argues significance under Criterion C in the area of Engineering as one of the earliest bridges designed by David Henry Overman, an Ohio bridge engineer noted for artistry in bridge design. It is described as one of four remaining bridges from his first year of bridge design, and the only one expected to remain of his earliest, most intricate work. It also retains its original concrete railings.","narrative":"Carrying Ohio State Route 51 over the Portage River at Elmore, this reinforced concrete bridge was built in 1926 and 1927 for $50,000. It has three closed spandrel arches, a total length of 282 feet and a 30-foot roadway. Its piers are anchored in limestone bedrock at a historic crossing with shallow rapids, and rounded pier bases guide water and ice. Concrete railings with beveled edges rest on open balustrades of modified Gothic design. The bridge was designed by David Henry Overman, who later became Chief Engineer of Bridges for Ohio. It is one of four surviving bridges from his first year of bridge design, and two of the others were scheduled for replacement, leaving this one as the best example of his earliest and most intricate work. Its original concrete railings are unusual for the period. Although scarred, it remains structurally sound. Original lantern posts were replaced around 1965 and the sidewalks were altered in the mid-1930s.","period_of_significance":"1926-1927","architect_builder":"Architect: Overman, David Henry; Builder: Gluss Brothers, Hamilton, OH","architectural_style":"OTHER: closed spandrel concrete arch","criteria":["C"],"status_note":"Described as scarred but still structurally sound; the highway department had marked areas for repair in 1993 photographs.","vacant_flag":null,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:52:07.357532-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_OH/94000239.pdf"},"photo":null,"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71990847","wikipedia":null,"wikidata":null},"indexable":true,"url":"https://nationalhistoricalregister.com/ohio/ottawa-county/ohio-state-route-51-bridge-over-the-portage-river-94000239/"}