Unicon I (which was called “International Unicycling Convention”) had no Trials. Nobody would think of unicycle trials for over ten years. It was all track racing, Freestyle, and basketball. There was no Standard Skill (there might have been a compulsory artistic event) and nothing on dirt. All competition events were held indoors and the convention was three days long.
The first “competitive” Trials-ish event was held at the 1998 California Mountain Unicycle Weekend. It was very basic; a challenging ride down a bumpy rock beach to Jenkinson Lake, then back up to the starting point, with points off for dismounts. California Mountain Unicycle Weekend - Competitions
The first “real” uni Trials competition I’m aware of was at the 1999 USA Convention in Washington. I had the honor of coming in second to Kris Holm (it’s been downhill for me ever since).
Side note: The first Street competition I know anything about was held last year at the 2004 CA MUni Weekend at Lloyd Johnson’s house. I heard about a similar event held earlier in Conneticut, but I don’t know anything about that one.
http://www.unicycling.com/muni/2004/compete.htm
For your other question: Unicycles initially weren’t “created.” They probably started out as penny-farthings with the back wheel up in the air, and were followed by penny-farthings with the frame and rear wheel removed. Only after that did people probably start custom-making actual unicycles with seats instead of handlebars.
According to JeanPaul Jenack and/or old issues of the USA Newsletter (Bill Jenack), the first commercially available unicycles were made in the 1940s by Nissen, a company that I believe still makes gymnastic equipment like balance beams and parallel bars.
Now to read up on Unicon 13! We’ve got a trip to Europe to plan!