Does my 16-yr-old son need a passport book or a passport card to travel to Canada?

My now 16-yr-old son was born in Germany and needed a passport to return to the US. Since then all our passports are lost or missing. I am pretty sure

Source: http://www.us-passport-service-guide.com/does-my-16yrold-son-need-a-passport-book-or-a-passport-card-to-travel-to-canada.html

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