Allegheny River Lock and Dam No. 9
The pin is a point inside the NPS boundary polygon, not a surveyed location.
Why it's listed
Lock and Dam No. 9 sits on the east side of the Allegheny River in a rural setting, and it was built by the U.S. Army Corps of Engineers between 1937 and 1938. York Engineering and Construction served as contractor. The 56-by-360-foot lock lifts vessels 22 feet, the highest lift on the river, and its steel miter gates close against a concrete sill. The 918-foot dam rests on bedrock and carries water across its full length without a spillway. A terrace of river-dredged material extends about 0.6 miles downstream to provide a nine-foot channel to the lower gate. The lock was designed to give slackwater navigation to limestone quarries near East Brady, extending the navigation system upstream. Its operating machinery, powered by turbines, has been largely retained, and the lock is regarded as a representative example of the period's standard lock and dam design.
Significance in brief: The nomination argues the lock and dam are significant for their role in the Allegheny River slackwater navigation system, giving barge access to limestone quarries near East Brady. It also argues they are a representative example of lock and dam construction of 1937-1938, retaining original appearance, machinery and function.
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 00000403, listed April 21, 2000. Summary generated October 2026 (model claude-haiku-5-5, prompt v1.1-2026-10-29, confidence medium).
Key facts
| Address | Terminus of PA 1004, 0.2 mi. N of T488, Widnoon |
|---|---|
| County | Armstrong County |
| Listed | April 21, 2000 |
| Reference number | 00000403 |
| Resource type | Structure |
| Period of significance | 1903-1948 |
| Architect / builder | York Engineering and Construction (contractor) |
| Architectural style | Late 19th and early 20th century revival |
| Criteria |
|
| Areas of significance | Transportation, Maritime History, Architecture, Engineering |
| Level of significance | State |
| Status (as stated in the nomination) | In operation; the hydroelectric plant was added in 1990, the operations building was pargeted circa 1990, and the heating system was converted to gas in 1964. |
| Acreage | 59.5 |
| Coordinates | 40.95367, -79.54631 (NPS GIS) |
What listing means for this property
For a publicly owned building or structure, listing mainly matters when federal funds, permits or licences are involved: projects then go through Section 106 review so effects on the property are considered. Listing also strengthens applications for preservation grants and, for leased income-producing uses, can enable the federal rehabilitation tax credit.
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 00000403.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q4731342
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.