I'm going to Canada and the States in the fall but I have a question about the border control. In October, I will be crossing the Canada-US border by train and I will then be entering the States for the first time in my trip, so I was wondering, how does it work with the visa/ESTA thing? Is it checked in the train, or before you board, when you get off..? What do I need to have with me in the train? I've checked the various border control websites but I can't seem to find this procedure. Can anyone help me?