thats what i thought. i just looked it up for anyone who is curious and doesnt have a passport, because i know Ski_Unit_19 was asking about this.
"ENTRY/EXIT REQUIREMENTS: For further information on entry requirements, travelers may contact the Embassy of Canada at 501 Pennsylvania Avenue NW, Washington, D.C. 20001, tel. (202) 682-1740, or the Canadian consulates in Buffalo, Detroit, Los Angeles, New York or Seattle. The Canadian Embassy's website is: http://www.canadianembassy.org/
Land and sea travelers are encouraged to have a valid U.S. passport. If they do not have a passport, they should be prepared to provide a government-issued photo ID (e.g. Driver's License) and proof of U.S. citizenship such as a U.S. birth or naturalization certificate.
U.S. citizens entering Canada from a third country must have a valid U.S. passport. A visa is not required for U.S. citizens to visit Canada of up to 180 days. Anyone seeking to enter Canada for any purpose besides a visit, (e.g. to work, study or immigrate) should contact the Canadian Embassy or nearest consulate prior to travel. Anyone with a criminal record (including some misdemeanors such as Driving While Impaired (DWI) charges) may be excluded or removed from Canada, and should contact the Canadian Embassy or nearest Canadian consulate well in advance of any planned travel for further processing, which may take some time."