Allegheny River Lock and Dam No. 6
Why it's listed
Built on the west bank of the Allegheny River about 36 miles upstream from its mouth, this lock and dam complex was constructed by the U.S. Army Corps of Engineers in 1927-1928. The lock measures 56 by 360 feet and lifts vessels 12.4 feet. Its 992-foot fixed-crest dam, roughly 20 feet high, rests on timber piles and stone-filled cribbing, with the dam portion built by Dravo Corporation. A two-story operations building houses hydraulic pumps driven by water turbines, which operated the lock's gates and valves. Two identical two-story tan brick locktenders' houses stand on the site. The facility opened on October 10, 1928, and formed part of a slackwater system giving commercial barges access to 72 miles of the river, including the Pittsburgh Plate Glass mills at Ford City. It is also valued as a well-preserved example of lock and dam construction from this period, retaining much of its original machinery and layout.
Significance in brief: The nomination argues the lock and dam are significant under Criterion A as part of the integral slackwater system that gave commercial barge access to 72 miles of the Allegheny River, including access to the Pittsburgh Plate Glass mills at Ford City. It also argues Criterion C significance as a representative example of lock and dam construction of 1927-1928 that retains its 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 00000400, listed April 21, 2000. Summary generated October 2026 (model claude-haiku-5-5, prompt v1.1-2026-10-29, confidence high).
Key facts
| Address | 1258 River Rd., Freeport |
|---|---|
| County | Armstrong County |
| Listed | April 21, 2000 |
| Reference number | 00000400 |
| Resource type | Structure |
| Period of significance | 1903-1938 |
| Architect / builder | Dam - Dravo Corporation; Lock - Corps of Engineers |
| Architectural style | Late Nineteenth and Early Twentieth Century Revival |
| Criteria |
|
| Areas of significance | Transportation, Maritime History, Architecture, Engineering |
| Level of significance | State |
| Status (as stated in the nomination) | Lock and dam remain in operation; the modern hydroelectric plant on the east side was added in 1988 and the operations building's original windows have been replaced; the locktenders' houses are presently vacant. |
| Acreage | 49.6 |
| Coordinates | 40.71814, -79.57912 (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 00000400.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q4731339
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.