In the United States, I’d probably name Oregon City, the famous end of the Oregon Trail and the first city founded west of the Rocky Mountains during the pioneer era. Its population is only 37,000.
In France it might be Y (population : 89), famous for having a one-letter name. Far from “anyone can still instantly recognise the name” but still probably much more well-known than any other town this size.
Otherwise idk, feels like the only french city everyone would instantly recognise the name of is Paris tbh.