Since the mound was moved to it's present distance

[kairos12]

no teenager has every won 20 games. Dwight Gooden won 24 when he was 20 years old.

[Beakybird]

1. When was it moved?

[kairos12]

2. It was moved from 50 feet to

60 feet 6 inches in 1893.

[WestMichRad]

3. Hardly surprising

Winning 20 or more in a single season has always been unusual and requires a degree of luck. Also is generally only achieved by very crafty pitchers who know how to mix up their pitches to keep hitters off balance. The young studs who make the majors before turning 20 are generally guys with awesome fastballs and they soon find out that in the majors, most of the hitters can make a good living hitting fastballs, so to beat them you need another very good pitch in your arsenal. It takes the young studs a bit of time to make the adjustment.... and then they're no longer teenagers!

The Doc had the ability to not only bring the heat, but he knew how to use his breaking ball very effectively. A rare talent he was!