President George Bush declared the Games open before the US national anthem was sung.
A spectacular show then took place, showing many scenes from American history.
Flame lit by ice hockey stars
There big cheers from the crowd for the parade of the 77 nations taking part, but the loudest cheers were for countries like Bermuda, Cameroon, Fiji and Jamaica - who aren't known for Winter Olympics success.
The Olympic flame was lit by members of the US ice hockey team from 1980, who famously defeated rivals Russia to win gold.