How the triathlon was invented

On September 25th, 1974, the first triathlon was held at Mission Bay in San Diego. Jack Johnston was one of the organizers of this seminal event, and tells the story on RunthePlanet.com:

First triathlon
First triathlon
In 1971, at age 35, I joined millions of other Americans in the jogging craze. As was the case with so many others, I'd been growing increasingly disgusted with my ever-expanding waistline and general physical deterioration. One thing led to another, and before I knew it I was competing in road races, which at that time, were relatively small (and inexpensive) affairs. My previous athletic career had been eight years as a high school and college swimmer. Despite being named to the 1957 Collegiate and AAU All-American teams in the 100 yard breast stroke, my overall performances had been rather mediocre. After a year or so of competitive running, I was still struggling to regain my athletic mediocrity. Then, in 1973, I heard about the "Dave Pain Birthday Biathlon", to be staged for the second time on July 28. A 4.5 mile run followed by what was billed as a quarter-mile swim (the actual distance was between 200 and 300 yards). My race! I thought. How many of these runners can swim? I found out. I can't remember my exact place, and the full results aren't available, but I think I came in somewhere around fourteenth. Nothing to write home about, but a lot better than I'd been doing in road races.
 
In much better shape the following year, I broke into the top ten. That rather modest success got me to thinking, There should be more of these races, and the swim should be longer. Someone else wasn't going to do it. If I wanted it to happen, I had to make it happen. I conceived of a run-swim biathlon with equal emphasis on the two disciplines, and several alternate legs. The initial run could be done in racing shoes, but subsequent running legs would have to be barefoot on a suitable surface (grass or sand). The Fiesta Island area of Mission Bay, where Dave Pain's race had been staged, was almost perfect. I designed a course, then called Bill Stock, the San Diego Track Club Calendar Chairman, and told him of my plans. He said he would put it on the calendar, and the rest was up to me. As an afterthought, he suggested I call Don Shanahan, who also had some strange event in mind. Maybe we could combine our ideas so there wouldn't be too many "weird" races on the schedule. I called Don and he told me that he wanted to include a biking leg. I wasn't too thrilled with the suggestion, having never cycled competitively (I didn't even own a bike). But what the hell, I thought, let's go for it. We decided to call the event the "Mission Bay Triathlon".