As a green card holder do you need a passport to travel Mexico and back to the USA?

Follow the link below to the Canadian government site concerning this question and scroll to the bottom where there are three buttons that address crossings by air (plane), land (car) or water (boat). Suffice to say, having a passport is a great convenience and satisfies the requirements of all three.

Concerning air: as of January 2007, a passport has become required for entry Concerning land: Photo ID plus a birth certificate (under 18 need only present a birth certificate) is currently still an option, but a passport will become required as of June 1, 2009. Concerning water: same requirements and future as land travel. Please follow the link for a more thorough treatment on rules, regulations and exceptions.