To both Tims,
One-man games in large urban areas such as the one I live in are very commonplace. There are simply way too many games that need coverage to always provide two officials. While some leagues request only one umpire, many request two, but on occasion, we can only provide one. When I first began umpiring in 1986, about 90% of my first year games were solo jobs. My very first baseball (I had already worked basketball and softball) game was a LL Majors game that I worked alone.
Our association has a good training program, with classroom instruction and field clinics. However, when I started, it was already April, so I just jumped in after one meeting and started working. I convinced the assignor that I could handle it, and I did just fine.
Tee, what would you have done back in the days where the umpire wore a top hat and tails, and sat perched on a tall stool? One-man mechanics, buddy.