Dennis writes-

CP express reefers are relatively common in photos of Soo Line
passenger trains, surprisingly often in No. 1 & 2 close to Chicago.
The story I've heard is they were carrying fish from the lakes
around the Winnipeg area to be used to prepare Lox for Chicago's
rather large Jewish community. Soo 1 & 2 made a good connection with
109 and 110, The Winnipeger, in St. Paul Union Depot, with an
express car also going through.

Dennis, I believe that you must mean gefilte fish, not lox (salmon).
Such fish (gefilte) usually has to be Kosher where a Rabbi makes an
attestation at the time the fish is killed and processed. My knowledge
of this arcane fish industry at that time is that such attestation was
almost almost always made nearer the point of consumption, such that
shipment of such fish- most commonly carp- had to be made live. This
required at that time cars with recirculating tanks (usually baggage
cars) with messengers on board to look after things. I know personally
examples on the Milwaukee (Milwaukee, NYC, and B&O baggage cars

In this regard, I am doubtful about such fish (processed) from
Manitoba being shipped to Chicago for such purposes.

However, I would well believe that these cars were carrying fresh
Pickerel (English Canada), Walleye Pike (the rest of the world)- same
delectable fish, of which the massive Lakes Manitoba and Winnipeg
still to this day support large commercial fisheries. Whitefish, a
still-prolific fish in Manitoba, and used at times for gefilte fish,
could also have been shipped. However, in steam era times, the Lake
Michigan whitefish fishery was still very active, and the lower
Chicago River would have numbers of commercial fishing boats lined up
hawking whitefish over their rails to eagerly awaiting buyers (my
father among them). Why ship coals to Newcastle?

Nowadays, this industry has changed. Rabbis are now hired to be at the
point of catch-and-processing, and the shipment of live fish for
gefilte fish has all but disappeared. I was once asked by a neighbor
fishery-business property owner in Iowa whether or not I was Jewish;
and if I was, I could earn $60,000/year to help my retirement by
becoming a rabbi and sitting for a few hours to attest to each live
fish at their moment of doom! I told him, regretfully, that I could
not qualify, but that he was very thoughtful to think of me.

Denny

Denny S. Anspach, MD
Sacramento