A passport (or NEXUS card) is required to cross the border by air. This applies if your trip includes a flight between a Canadian and American airport. However, if you have an Enhanced Driver's Licence or U.S. Passport Card, you can still drive across the Canada/U.S. border and take a domestic flight (e.g. drive Buffalo to Toronto, fly round-trip Toronto/Winnipeg, drive back to Buffalo). From CBSA " If you are a citizen of the United States, you do not need a passport to enter Canada. However, you should carry proof of your citizenship, such as a birth certificate, certificate of citizenship or naturalization, as well as photo identification. " But you will need a Passport Book (if traveling by air), or Passport Card (if traveling by land) to re-enter the United States, so the border agents will check that you have one to be able to re-enter the U.S. For more details, see Canada Border Services Agency U.S. citizens with a criminal...
A passport (or NEXUS card) is required to cross the border by air. This applies if your trip includes a flight between a Canadian and American airport. However, if you have an Enhanced Driver's Licence or U.S. Passport Card, you can still drive across the Canada/U.S. border and take a domestic flight (e.g. drive Buffalo to Toronto, fly round-trip Toronto/Winnipeg, drive back to Buffalo). From CBSA " If you are a citizen of the United States, you do not need a passport to enter Canada. However, you should carry proof of your citizenship, such as a birth certificate, certificate of citizenship or naturalization, as well as photo identification. " But you will need a Passport Book (if traveling by air), or Passport Card (if traveling by land) to re-enter the United States, so the border agents will check that you have one to be able to re-enter the U.S. For more details, see Canada Border Services Agency U.S. citizens with a criminal...