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.
Also consider that Roquefort-sur-Soulzon, of cheese fame, has 528 inhabitants.
Even without considering cheese villages (somebody mentioned Roquefort, I was thinking of Gruyere, France clocking in at about 100 inhabitants), I believe Verdun would be just as known and is smaller at a population of around 17000.
Mont Saint-Michel, pop. 25
Chamonix of also a good contender with a population of 9000 habitants
Admittedly my WW2 history knowledge is quite lacking, but I don’t recognise Vichy because of the war stuff.
But I do recognise Vichy! Because we have a sub-type of mineral water in Sweden that is named after Vichy, “Vichyvatten”. Wikipedia tells me the original was from a spring near Vichy, hence the name.
Nice one, didn’t think of that ! I suggested the one-letter town Y (population : 89), which is obviously much less well-known, but is also much smaller.
Edit : just realised, the airport city Roissy-en-France at under 3k inhabitants is a huge contender too that wasn’t mentioned