US Chess Open

How does one get to participate in the US Open? Just show up and pay the entry fee? I never hear of any walks ons winning the open. Its always the same cast of characters, all titled, always the same ones you read about in the chess magazines and blogs

I did not realize they were two different things..thanks for clearing that up.

Just curious how does one qualify for the US Championship then. Is it just based on ratings? Is there a special tournament schedule you need to complete? 

The top x amount of players by rating qualify for the US championship, and there are a few other tournaments that the winner automatically qualifies for the closed invitational (the US Junior Closed being one of them, with IM Akshat Chandra winning it this last edition.)