Effective June 2009, if you are travelling between the United States and Canada, Mexico, Central and South America, the Caribbean, and Bermuda, and you are a U.S. or Canadian citizen age 19 and older, you must present a passport or other approved secure document denoting citizenship and identity for all travel into the United States.
If you are a U.S. citizen, you may be eligible for an Enhanced Driver’s License (EDL) or NEXUS card, which have been formally identified as acceptable documentation requirements to meet the requirements for proof of citizenship to re-enter the U.S. from Canada.
More information is available at getapassportnow.com and www.atnexus.com, as well as at the American Department of Homeland Security website: www.cbp.gov/xp/cgov/travel/vacation/kbyg/
Visitors to Canada from countries other than the U.S. must have a valid passport to enter Canada and may require other documentation. For more information, go to the Canadian Border Service Agency website: www.cbsa-asfc.gc.ca