Der Kanton is more or less a state/province in Switzerland. too small to be really states, sometimes too big for a province. So it is not common in Germany, but it is in Switzerland. their political system revolves around the relative independence of the "cantons"
I guess Duolingo is trying to be inclusive of Swiss culture. It seems a fairly obscure word to throw in though. Thanks!
Is "Kanton" a common word in Germany? I certainly don't come across "Canon" much in English.