If you are a citizen of the United States, you do not need a passport to enter into Canada or the U.S when travelling by land or sea. However, you should carry proof of your citizenship, such as a birth certificate, certificate of citizenship or naturalization, as well as a photo ID. If you are a permanent resident of the U.S., you should bring your Permanent Resident Card (i.d. green card) with you.
Effective January 8, 2007 US citizens travelling by air between the United States and Canada will be required to present a valid US passport, Air Nexus card, or US Coast Gaurd Merchant Mariner Document.
For more information visit www.travel.state.gov or www.cbsa.gc.ca
