If you are traveling from outside Canada, you may need a visa to enter Canada. Please refer to the Government of Canada site (http://www.cic.gc.ca/english/visit/visas.asp) for instructions on how and who needs to apply for a Visitor’s Visa to come to Canada.
US citizens carrying a valid US Passport do not require a Visa to come to Canada. Residents of the US who carry a passport from a country listed on the Government of Canada site will need an Invitation Letter from the Conference Chair to attach to their Visitor’s Visa Application. Please give sufficient time for processing. See: http://www.cic.gc.ca/english/information/applications/index.asp for an estimate of processing times.
As of March 15, 2016 any delegates from visa-exempt countries will need to apply for an eTA. The eTA costs $7.00 and allows for pre-screening of visa exempt nationals. Please see the link for details related to the eTA. http://www.cic.gc.ca/english/visit/eta.asp