Yeah, the average winters back then were substantially colder so as you can imagine, the volcanic winters back then were pretty mind-boggling. 1783-84 is the most noteworthy example following the Laki eruption in Iceland. The Chesapeake Bay was frozen over completely up to its mouth and sailors reported seeing large blocks of ice in the Gulf of Mexico a hundred miles offshore, with the Mississippi frozen over at New Orleans.
Kinda went down the rabbit hole looking at below zero days, and it's striking to see the difference between Chicago and Detroit. There have only been 11 calendar years in which Chicago has failed to drop below zero, with 10 of them occurring before 1964 when the observation site was at Midway Airport or somewhere else closer to the lake. Meanwhile, Detroit has had 42 calendar years that have not been below zero.
These 2 cities lie essentially at the same latitude, so other than siting issues that could make a difference in borderline situations, this basically comes down to the modifying effects of Lake Michigan. Arctic outbreaks typically come in on W or NW winds, so there is no lake modification of airmasses for Chicago in those situations.