History Link has an article on the opening of the Seattle Worlds Fair April 21, 1962, here.
This was the first worlds fair I attended. My parents went during the summer and we stayed with Clarence and Minnie Ruud. They were our neighbors in Spokane for many years and when Clarence retired he moved to just north of Seattle to be close to his son. I am going to post a bunch of pictures from my moms scrapbook over the next week or so.