Entry into Canada: Canadian law requires that all persons entering Canada carry both proof of citizenship and proof of identity. A valid U.S. passport, passport card, or NEXUS card satisfies these requirements for U.S. citizens.
Children under 16 need only present proof of U.S. citizenship.
Entry into the United States: When traveling by air from Canada, U.S. citizens are required by U.S. law to present a U.S. passport book. A few exceptions to this rule and a full list of documents that can be used at land and sea borders are provided on the
U.S. Customs and Border Protection (CBP) website.