Locals call the top of the Keweenaw “Copper Island,” and the waterway that cuts it off runs 25 miles. Most of that was already there. The man-made part is the western cut, from Portage Lake out to Lake Superior, and finishing it took more than a million cubic yards of earth.
Transcript
Locals call the top of the Keweenaw Copper Island. A waterway cuts it off from the rest of the U.P.
It runs twenty-five miles. Most of it was already there. Portage Lake and the Portage River did most of the work.
What crews cut was the western end, from Portage Lake out to Lake Superior.
Initial construction moved 1,048,660 cubic yards of earth. By 1872 all that stood in the way of a complete bisection was forty-nine thousand cubic yards of hardpan.
Dredging had started back in 1864. The Army Corps took the waterway over in 1891.
Connect the lake to Lake Superior and boats could cut straight across instead of going all the way around the tip.
So the island’s real. It just took a lot less shovel than you’d think.
The receipts
- Michigan Country Lines: “The 25-mile partially man-made Keweenaw Waterway bisects the Keweenaw Peninsula.”
- Michigan Tech, Military History of the Upper Great Lakes: dredging began in 1864; initial construction removed 1,048,660 cubic yards of earth; by 1872, 49,000 cubic yards of hardpan remained before the peninsula was fully bisected. The U.S. Army Corps of Engineers took the waterway over in 1891 after Congress purchased it.
- Wikipedia, Keweenaw Waterway: the part of the peninsula north of the waterway is known locally as “Copper Island.”
What we won’t say: that the dug section is exactly two and a half miles. That figure appears on one uncited hobbyist page and on no Corps document we could find, so it is out. We also won’t give a completion year: sources put it at 1873 and at 1874 and we cannot settle it.
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Sources, credits, and reporting details
Sources & accountability
How this story was reported
Editorial methodArchival synthesis
Last verifiedSep. 13, 2026
Corrections statusNo material correction note is recorded on this article.
AI assistanceResearched and drafted with AI tools. Reviewed and approved by editor Keegan O’Brien.
Verification note: RESOLVED Sep 13, 2026. The headline number could not be sourced and has been removed. Old headline: "The Keweenaw’s Copper Island Canal Is 25 Miles Long. Only 2.5 Were Actually Dug." The 25 miles holds and is independently confirmed. The 2.5 does not. Checked directly this session: Wikipedia’s Keweenaw Waterway article gives no mileage at all, only a 25-foot depth. The American Canal Society’s Keweenaw index page is an unfilled template. Michigan Tech’s Military History of the Upper Great Lakes gives excavation volumes, not miles. The USACE Detroit District page is unreachable, a TLS certificate failure on their side. The 5 / 17.5 / 2.5 split appears only on Lighthousefriends.com, which cites nothing for it: its reference list is three general Annual Reports with no attribution to the figures. The whole article turned on 2.5 of 25. Rebuilt on what is attributable. Michigan Country Lines independently gives "The 25-mile partially man-made Keweenaw Waterway." Michigan Tech gives 1,048,660 cubic yards of earth removed in initial construction and 49,000 cubic yards of hardpan remaining by 1872, which is more vivid than the mileage fraction was and is actually sourced. The structural point, that most of the waterway is natural lake and river and the cut is at the western end, is uncontested. Completion year also dropped. Sources conflict: Lighthousefriends says 1873, Michigan Country Lines says the western canal was completed 1874, and we had published 1873. The cubic-yard framing sidesteps it. The 1864 dredging start and the 1891 Corps takeover are both from Michigan Tech. New headline: "Copper Island Is a Real Island. Finishing It Took Crews More Than a Million Cubic Yards of Earth."
Primary sources
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Keweenaw Waterway, MI — U.S. Army Corps of Engineers, Detroit District
Accessed Sep. 13, 2026.
Confirms the 25 mile total from a primary federal source. Does not break out how much was dug.
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Keweenaw Waterway, Michigan — U.S. Army Corps of Engineers, Great Lakes and Ohio River Division
Accessed Sep. 13, 2026.
Included as independent corroboration of the one number that is solid.
Additional reporting
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Keweenaw Waterway Upper Entrance Lighthouse, Michigan — Lighthousefriends.com
Accessed Sep. 13, 2026.
This is the only source for the headline number and it is an enthusiast history site, not a government record. Replace with a primary source or soften the claim.
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Keweenaw Waterway — Wikipedia
Accessed Sep. 13, 2026. CC BY-SA 4.0.
Tertiary. Carries the Copper Island framing and the construction start only.
Photo and media credits
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Keweenaw Waterway north end.jpg (featured image) — U.S. Army Corps of Engineers Digital Visual Library, via Wikimedia Commons
Featured image record. Accessed Sep. 13, 2026. Public domain, U.S. federal government work.
File page confirmed via the Commons API. Author reads U.S. Army Corps of Engineers, photographer not specified or unknown; credit reads U.S. Army Corps of Engineers Digital Visual Library; licence public domain. Rights are clear. The article itself still carries no caption, credit or alt text for this image and needs them added.
