Do you need a passport to go to Canada?

Passports from US citizens crossing Canadian and Mexican borders by land or sea in have been required since June 2009. Yes, you need a passport to go to any other country that's not your own
Ideally Yes. Since visiting Canada if you are not Canadian is an international Travel. This means the immigration will check you if you are eligible to Enter. This calls for a proof of your citizenship and identity both of which a passport fulfills. It is safer if not preferred to travel with you passport with you.