Do I need a passport to travel to Canada?
Canadian port of entry
Entry into Canada is determined by the Canadian Border Services Agency (CBSA) in accordance with Canadian law requiring that all persons entering Canada carry both proof of citizenship and proof of identity. A valid US passport, passport card or NEXUS card (see below) satisfies these requirements for US citizens.
Both the US and Canadian governments urge frequent travelers to join the NEXUS trusted traveler program. NEXUS members receive a special travel card that allows expedited border crossings for both private and commercial travelers through both US and Canadian border controls.
Coming back to the US
When returning to the United States from Canada, please know that all US citizens are required to present a valid US passport to enter or re-enter the United States via air. For entry into the United States via land or sea borders, US citizens must present either a US passport, passport card, NEXUS card, Enhanced Drivers License or other Western Hemisphere Travel Initiative (WHTI)-compliant document.
Passport Exception for children
The only exception to the requirement that all US citizens must present a passport upon entry to the US is for children under the age of 16 (or under 19, if traveling with a school, religious or other youth group) who need only present a birth certificate (original, photocopy or certified copy), Consular Report of Birth Abroad or naturalization certificate.
Other information for children
Parents who share custody of their children should carry copies of the legal custody documents and are recommended to have a letter of authorization from the other custodial parent to take the child on a trip out of the country. This letter will confirm that the child is not being abducted or taken against his/her will. The parents' full name, address and telephone number should be included in the letter of authorization.