Colwell Cut Viaduct
Also known as: Hogback Hill Bridge
Why it's listed
Built in 1922 by the Concrete Steel Bridge Company of Clarksburg, West Virginia, the Colwell Cut Viaduct is an open-spandrel concrete arch bridge that carries vehicular traffic over the Pittsburgh & Shawmut railroad in rural Mahoning Township, Armstrong County. Its main arch spans 128 feet, placing it within the range of the open-spandrel arches in the nominated group, which run from about 40 to 200 feet. The bridge is known locally as Hogback Hill Bridge and is listed as Structure No. 99 in its inventory records. Its boundary covers the superstructure and substructure within the outside corners of the wing walls, and the site is less than one acre. Its importance lies in engineering. It is one of only four nominated concrete arch bridges in western Pennsylvania and one of only a few nominated bridges in the region that represent this widely used concrete type. In 1975 its parapets and deck were replaced, which reduced its original integrity.
Significance in brief: The nomination describes the bridge as a typical example of the open-spandrel concrete arch type. Its 128-foot main arch is of moderate length within the nominated group. It is one of only four nominated concrete arch bridges in western Pennsylvania and one of only a few nominated bridges to exemplify this type in that region. The area of significance is engineering.
Machine-generated summary. This summary was generated by a language model from the official nomination document and has not been reviewed line by line by an editor. It may contain errors. Check the source document before relying on any detail. Source: nomination document (PDF) · National Archives catalog entry. NRHP reference 88000796, listed June 22, 1988. Summary generated October 2026 (model claude-haiku-5-5, prompt v1.1-2026-10-29, confidence medium).
Key facts
| Address | LR 66 over Pittsburgh & Shawmut RR, Seminole |
|---|---|
| County | Armstrong County |
| Listed | June 22, 1988 |
| Reference number | 88000796 |
| Resource type | Structure |
| Period of significance | 1922 |
| Architect / builder | Unknown (designer/engineer); Concrete Steel Bridge Co. (bridge company) |
| Criteria |
|
| Areas of significance | Engineering |
| Level of significance | State |
| Status (as stated in the nomination) | Parapets and deck were replaced; the structure was altered in 1975. |
| Acreage | 0.9 |
| Coordinates | 40.93705, -79.36290 (NPS GIS) |
What listing means for this property
National Register listing is honorary: it recognises significance and does not restrict what a private owner may do without federal money or permits. It unlocks the 20% federal rehabilitation tax credit for income-producing buildings, state credits in many states, and Section 106 review when federal agencies are involved. See what listing means in practice.
General information, not legal or tax advice. Rules change; confirm with your State Historic Preservation Office or a qualified adviser.
Sources and further reading
- National Park Service, National Register of Historic Places database (snapshot May 2026), reference 88000796.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q5150319
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.