Potomac Canal Historic District
Also known as: Patowmack Canal Historic District
Why it's listed
Within Great Falls Park in Fairfax County, Virginia, lie the remains of a canal built to carry boats around the Great Falls of the Potomac. The Patowmack Canal Company worked on it from 1785 to 1802. The route runs about three-quarters of a mile and once had a wing dam, guard gates, a two-acre holding basin and five locks. The lowest locks were blasted from solid rock with black powder in hand-drilled holes. The canal was part of a plan, backed by George Washington, to make the Potomac navigable toward the Ohio country, and Maryland and Virginia bought nearly half the company's shares. The company failed financially and dissolved in 1826. Nearby ruins include the planned town of Matildaville, founded by Henry Lee, along with mill and foundry sites, a log inn and a superintendent's house. Today the canal is a ruin, but it preserves significant evidence of early American canal engineering and state-backed commercial ambition.
Significance in brief: The canal was the largest of five skirting canals on the Potomac and an early, significant American engineering achievement, since canals with locks were uncommon at the time. Its lower locks were blasted from bedrock with black powder, one of the first uses of explosives in American engineering. It was one of the first state-financed internal improvements, promoted by George Washington, and it also includes the ruins of the speculative town of Matildaville.
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 79003038, listed October 18, 1979. Summary generated October 2026 (model claude-sonnet-5-5, prompt v1.0-2026-10-29, confidence medium).
Key facts
| Address | E of Great Falls, Great Falls |
|---|---|
| County | Fairfax (city and county) |
| Listed | October 18, 1979 |
| Reference number | 79003038 |
| Resource type | District |
| Period of significance | 1785-1830 |
| Architect / builder | Patowmack Canal Company; John Rumsey appears to have been the principal engineer |
| Areas of significance | Engineering, Politics/Government |
| Level of significance | National |
| National Historic Landmark | Yes, designated December 17, 1982 |
| Status (as stated in the nomination) | Described as in ruins: much of the canal bed is filled with debris and silt, the lock gates were dismantled in 1830, and the associated structures survive only as foundations or ruins. |
| Acreage | 25 |
| Coordinates | 38.99666, -77.25275 (NPS GIS) |
What listing means for this property
This is a historic district. Buildings within its boundary are either contributing (they add to the district's significance) or non-contributing. Owners of contributing income-producing buildings can claim the 20% federal rehabilitation tax credit; homeowners should look at state credits. National Register districts impose no design review by themselves; a local historic district ordinance, if one exists, does (the difference explained).
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 79003038.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q7235044
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.