Thunder Bay is a city on the northwestern shore of Lake Superior in Ontario, Canada, and the most populous municipality in Northwestern Ontario, with a population of 108,843 according to the 2021 Canadian census. Today it is a working port city and regional hub, but during World War I it was the unlikely site of a remarkable — and ultimately tragic — shipbuilding experiment. The Canadian Car and Foundry Company, based here, was contracted by the French Navy to construct 12 minesweepers despite having no prior shipbuilding experience whatsoever; as one expert tells Gates on camera, they had built railroad boxcars, not ships. Nine of the vessels departed Thunder Bay and reached the Atlantic without incident, but three — the Inkerman, the Cerisoles, and the Sebastopol — left port on November 23, 1918, and sailed into one of Lake Superior's notorious storms. Gates investigated Thunder Bay as the departure point of those three doomed ships, tracing the beginning of a mystery that has never been fully resolved.
Canadian Car and Foundry Company established as a major industrial manufacturer in Thunder Bay, primarily producing railroad rolling stock
Canadian Car and Foundry Company contracted by the French Navy to build 12 minesweepers in six months, despite no prior shipbuilding experience
Nine of the 12 minesweepers depart Thunder Bay and reach the Atlantic uneventfully
The Inkerman, Cerisoles, and Sebastopol depart Thunder Bay under the command of Marcel Leclerc; two of the three are lost in a violent Lake Superior storm that night
Josh Gates investigates Thunder Bay and the lost minesweepers in Expedition Unknown S12E05, "Chasing Bonnie and Clyde"
In S12E05, Gates sits down with an expert — whose name is not confirmed in the available transcript — who explains why the French Navy turned to an inland Canadian manufacturer in the first place: French shipyards were overwhelmed by wartime demand, and the Canadian Car and Foundry Company in Thunder Bay agreed to deliver 12 fully functional minesweepers in just six months. The expert emphasizes that this was an extraordinary industrial pivot, from building railroad boxcars to constructing ocean-going naval vessels under wartime pressure.
Mainstream historical accounts confirm the broad outlines of this story. Minesweepers of this era were relatively small craft designed to drag cables or trawls beneath enemy contact mines, severing their anchor lines so the mines could float to the surface and be destroyed by onboard guns. Building them required new expertise in hull design, buoyancy, and marine engineering — skills the Canadian Car Company had to develop essentially from scratch. That nine of the twelve vessels completed the journey to the Atlantic successfully speaks to a genuine, if hard-won, industrial achievement.
The fate of the Inkerman and the Cerisoles remains one of Lake Superior's enduring mysteries. The lake is notorious among maritime historians for the ferocity and unpredictability of its storms; it sits at an elevation that generates its own weather systems, and its cold waters offer little margin for error. The episode draws on Captain Leclerc's own account from the Sebastopol, which described 50-mile-an-hour winds and 18-foot waves — conditions that could overwhelm small, newly built vessels crewed by men unfamiliar with Great Lakes sailing.
What Gates' episode contributes is a vivid reconstruction of the departure from Thunder Bay and the human drama behind the storm — the calm morning, the confident send-off from the port, and the rapid deterioration that followed. The episode frames Thunder Bay not as a destination in itself but as the starting point of a tragedy, inviting viewers to follow the ships' route into Lake Superior in search of answers that have eluded investigators for over a century.
Thunder Bay is the most populous municipality in Northwestern Ontario, with a population of 108,843 according to the 2021 Canadian census.
The Canadian Car and Foundry Company agreed to deliver 12 brand-new minesweepers in just six months — despite having no prior shipbuilding experience, having built railroad boxcars before the contract.
Nine of the 12 minesweepers built in Thunder Bay completed their journey to the Atlantic uneventfully; only the two lost ships, the Inkerman and the Cerisoles, have never been found.
Lake Superior's storms are notorious among maritime historians — the lake sits at an elevation that generates its own weather systems, and the episode describes conditions the night of November 23, 1918, as 50-mile-an-hour winds with 18-foot waves.
Thunder Bay is a major regional city with an airport, hotels, and infrastructure for visitors. The waterfront area along Lake Superior is generally accessible, and the city has local museums and heritage sites that touch on its industrial and maritime history. Visitors interested in the minesweeper story may find the local historical society and the Thunder Bay Museum useful starting points, though on-site interpretation of the Canadian Car and Foundry shipbuilding history is limited.
Thunder Bay itself is the regional hub; the nearest large city is Duluth, Minnesota, approximately 270 kilometers (170 miles) to the southwest across the border.
Summer months — June through August — offer the most comfortable weather and the best access to Lake Superior's waterfront. Winters in Thunder Bay are severe, with heavy snowfall and extreme cold, which is a reminder of just how unforgiving the lake's weather can be.
Lake Superior
Lake Superior is the body of water directly connected to the Thunder Bay minesweeper mystery — the Inkerman and Cerisoles vanished somewhere in its depths after departing Thunder Bay on November 23, 1918.
Lake Michigan
Lake Michigan is another Great Lakes site investigated by Gates, reflecting the recurring theme of shipwrecks and maritime mysteries in the inland sea system that includes Lake Superior.
Normandy Beaches, France
The Normandy Beaches episode connects thematically to WWI and WWII naval history, including the role of minesweepers and allied naval operations that form the broader context of the French Navy's wartime shipbuilding program.
Historical data sourced from Wikipedia