I flew to Calgary in July with my wife and infant son for the Stampede in early July. Everything I read said to make sure to bring the childs birth certificate for proof of identification. Going into Canada was a breeze. Customs agent asked us our nationality and said have fun at the Stampede. Going through customs to return to the US was tougher than any entrance after being in Europe. No problem with the baby identification but the agent was giving my wife and me a hard time over not having passports. I refuse to take a passport to Canada! We gave him drivers license and our Voter ID cards (voter ID is considered a suitable form of ID). He asked if we had any other ID and I responded that I thought you needed to be an American to vote in the US. He gave me a glaring look and passed us through.