Requirements for International Travel

Entry into Canada is solely determined by Canadian Border Services Agency (CBSA) officials in accordance with Canadian law, see http://www.cbsa.gc.ca for details.  Canadian law requires that all persons entering Canada must carry both proof of citizenship and identity.

If you are a citizen of the United States, you do not need a passport to enter Canada; however, you should carry proof of your citizenship such as a birth certificate, certificate of citizenship or naturalization or a Certificate of Indian Status, as well as a photo ID. If you are a permanent resident of the United States, you must bring your permanent resident card (i.e. green card) with you. For more information on admissibility into Canada, read the fact sheet called Managing Access to Canada. It is available on our Web site at www.cbsa.gc.ca.

ENTRY/EXIT REQUIREMENTS:  U.S. citizens traveling to Canada are required to show U.S. Government-issued photo ID and proof of U.S. citizenship, such as a birth certificate.

The U.S. Department of State recommends traveling with a valid U.S. passport to avoid delays or misunderstandings.  A lost or stolen passport is also easier to replace when outside of the United States than other evidence of citizenship.

http://gocanada.about.com/od/faqscrossingtheborde1/p/border_tips.htm

http://www.state.gov/travelandbusiness/