Traveling by Air
As of now a passport is required for air travel to or from Canada.
Traveling by Land or Sea
U.S. and Canadian citizens will need to present either a WHTI-compliant document, or a government-issued photo ID, such as a driver's license, plus proof of citizenship, such as a birth certificate. DHS also proposes to begin alternative procedures for U.S. and Canadian children at that time.
For detailed information about obtaining or renewing your U.S. passport, visit the U.S. Department of State, Passport Services Office, or access U.S. passport application services from the United States Postal Service.
For detailed information on entry requirements, including medical exams, working or studying in Canada, and what you are permitted to bring into Canada, visit the Canada Border Services Agency website.