Traveling to Toronto
Detailed information about traveling from the US to Canada can be found at http://www.cbsa-asfc.gc.ca/E/pub/cp/rc4161/rc4161-e.html. In summary, US citizens should carry, as proof of citizenship, a birth certificate plus picture ID. A passport is not necessary, but would certainly suffice as proof as citizenship. If you need to obtain a birth certificate, http://www.cdc.gov/nchs/howto/w2w/w2welcom.htm has links to info for all states.