St. Canard has technically never been stated to be located in Calisota. It has, however, been strongly implied to be a city nearby Duckburg, which is confirmed to be located in Calisota.
The name "Calisota" is a portmanteau of "California" and "Minnesota" invented by Carl Barks. It may have had a rival name in "Cauliflowernia". Despite the focus on California, Calisota is a "traveling" state, situated wherever the story needs it to be.