Bottom line: Since June 2009, everyone from every country arriving in Canada by air, land and sea has needed a passport or equivalent travel document. (Some exceptions apply to children's passport requirements). Besides an up-to-date passport, visitors may instead have an equivalent travel document, such as a NEXUS Card.
Best Advice: If you haven't already, apply now for your U.S. passport or an equivalent travel document.
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In Depth: Passport requirements have been a complicated and ever changing issue for U.S. travellers to Canada for the past few years due to the Western Hemisphere Travel Initiative (WHTI), which was introduced in 2004 by the U.S. government to strengthen U.S. border security and standardize travel documentation.
Visitors from any country other than the U.S. have always needed a passport to enter Canada. On the other hand, because of a friendly border crossing agreement between Canada and the United States, Canada Border Services did not require U.S. citizens to present a passport to enter Canada. This friendly border crossing agreement used to be mutual; however, now the WHTI requires that U.S. citizens have a passport to return home. In this way, passport requirements for Canada and U.S. borders are different on paper, but, are in practice, the same. Canada will not allow a U.S. citizen into the country who does not have the proper documentation to return home.
One thing is certain about passport requirements: the trend for essential travel documents, even between neighbouring countries like Canada and the U.S. and Mexico, is toward increased security and standardization. A passport - or equivalent travel document - is a must.
Don't wait! The U.S. application process is already backlogged. Apply online for your American passport now (PDF file) or learn what travel documents are acceptable substitutes for a passport.
For More Information:
Canada Border Services Agency OR The US Department of State