{"nrhp_refnum":"100000868","name":"Eldean Covered Bridge","other_names":[],"category":"structure","location":{"address":"Spanning Great Miami River at bypassed section of Eldean Rd. (CR 33)","address_restricted":false,"city":"Troy","county":"Miami County","state":"OH","lat":null,"lon":null,"geom_source":null},"listed_date":null,"is_nhl":true,"nhl_designated_date":"2016-12-23","areas_of_significance":["Engineering"],"significance_levels":[],"summary":{"what_it_is":"A two-span wooden covered bridge over the Great Miami River about one mile north of Troy in Concord-Staunton Townships, Miami County, Ohio, built in 1860 by James and William Hamilton.","why_significant":"It is the last covered bridge remaining in Miami County and one of only four still spanning the Great Miami River. It is the second longest covered bridge in Ohio. It is also a fine and now rare Ohio example of the Long truss and of Civil War era engineering.","narrative":"Spanning the Great Miami River about a mile north of Troy, Ohio, this two-span covered bridge was built in the summer of 1860 by James and William Hamilton, who operated a stone quarry near Piqua. It is 234 feet long and uses a 24-panel Long truss, an all-wooden design of boxed X's patented in 1830 and considered the first to rely on mathematical calculation. The timbers are white pine, likely shipped from Michigan by canal boat, and the diagonal plank flooring is unusual. Stone abutments and a pier carry the structure under a sheet metal roof. It is the last covered bridge in Miami County, one of four still crossing the Great Miami, and the second longest in Ohio. The county bypassed it in 1963 to preserve it as a historic site, adding a parking area and picnic shelter. Repairs were made in 1922, 1936 and the 1960s, yet its appearance has changed little.","period_of_significance":"1860 (19th Century)","architect_builder":"James and William Hamilton (builders)","architectural_style":"Long truss covered bridge","criteria":[],"status_note":"Bypassed by Miami County in 1963 and preserved as a historic site with a parking area and picnic shelter; condition listed as good.","vacant_flag":null,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:53:10.176145-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_OH/75001492.pdf"},"photo":null,"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":null,"wikipedia":null,"wikidata":null},"indexable":true,"url":"https://nationalhistoricalregister.com/ohio/miami-county/eldean-covered-bridge-100000868/"}