Sorry to be late to the game, and I believe all opinions have been offered and reconciled.
I will unconditionally state: Taxodium distichum is hardy into at least zone 4, because I have purchased, transported, and planted successfully 10" caliper Taxodium distichum 'Shawnee Brave' from a southern Wisconsin nursery to the thoroughbred horse farm in central Kentucky for which I used to manage the landscape. Four of these trees still grace the easternmost broodmare barn on that farm; they were planted in spring 1992.
The tree illustrated is unquestionably Taxodium distichum, for all the reasons mentioned. The leaf arrangement is in no way opposite, so it cannot be the similar Metasequoia glyptostroboides. I suspect Bald-cypress does well in metro Chicago due to the city's heat island effect, and its tolerant of saturated soils as well as its tolerance of droughty conditions and a wide range of soil types.
Taxodium distichum is native in Reelfoot Lake, which straddles the KY-TN state line. It also forms phenomenal specimens in southern Illinois swamps. Giant City State Park is near some of those exceptional stands, where it forms a swamp-wetland association with Nyssa aquatica. The Great Rivers Chapter of Holly Society of America has made regular visits to this interesting environment over the years that I've been a member.
Finally, this species ranges as far north as Maryland at Battle Creek Cypress Swamp. I had the pleasure of walking this property back in July 1991. I don't recommend visiting that time of year.
This species likely covered most of what is the temperate North American continent prior to the last glacial Ice Age, which eliminated everything in the path of mile-thick sheets of ice. As that insult retreated (which is still occurring), plants have moved northerly to reclaim the ground they once occupied. Thus, species like Taxodium distichum, Aesculus parviflora, Hydrangea quercifolia, and many more can be found happily growing in landscapes far north/colder than where European settlers and plantsmen found them in natural environments.